Physics: Unit 6-10 Tests

In an area in which electricity costs 8 cents/kilowatt-hour, a 5 kW clothes dryer runs for 90 minutes to dry a load of laundry. How much did it cost to dry these clothes?

$0.60

Compare and contrast the voltages and the currents in series and parallel circuits.

(1) In a series circuit, the current in each device is the same, and the sum of the voltage drops is equal to the source voltage. (2) In a parallel circuit, the voltage drop across each device is the same, and the sum of the currents through each loop equals the source current.

If 10^6 electrons are removed from an initially neutral pith ball, the charge on the pith ball is:

+1.60 x 10^-13 C.

The charge of one electron is -1.60 x 10^-19 C. If a neutral object loses 1.4 x 10^6 electrons, the charge on the object is:

+2.24 10^-13

A 2.0 m wire segment carrying a current of 0.60 A oriented parallel to a uniform magnetic field of 0.50 T experiences a force of what magnitude?

0.0 N

There are two balloons of charges +3.37 x 10^-6 C and -8.21 x 10^-6 C. The distance between the two balloons is 2.00 m. Determine the force between the two balloons.

0.0623 N

An electron moves north at a velocity of 4.5 × 10^4 m/s and has a magnetic force of 7.2 × 10^-18 N exerted on it. If the magnetic field points upward, what is the magnitude of the magnetic field?

1.0 mT

Find the magnitude and direction of the electric field at a point where a negative charge of 5.0 × 10^-8 C is placed. The charge experiences a force of 5.0 × 10^-2 N to the right.

1.0*10^6 N/C toward the left

A 20.0-W resistor and a 40.0-W resistor are connected in series across a battery. If the current is 2.00 A, what is the voltage of the battery?

1.20 × 10^2 V

Two point charges, initially 2 cm apart, are moved to a distance of 10 cm apart. By what factor does the resulting electric force between them change?

1/25

Two positive point charges are initially separated by a distance of 2 cm. If their separation is increased to 6 cm, the resultant electrical potential energy is equal to what factor multiplied by the initial electrical potential energy?

1/3

What is the quantity of charge that passes through a conductor when there is a current of 0.25 A for 10 minutes?

150 C

The distance between two slits in a double-slit experiment is 0.0050 mm. What is the angle between the central maximum and the second dark fringe in the interference pattern produced with light having a wavelength of 550 nm?

16°

If two light waves are out of phase, what is the largest amount by which their phases can differ?

180°

A string of holiday lights has ten bulbs of equal resistance connected in a series. When the string of lights is connected to a 120-V outlet, the current through the bulbs is 0.06 A. What is the resistance of each bulb?

2 x 10^2

What is the equivalent resistance for the resistors in the figure shown above?

2.2 Ω

A proton moves north at a velocity of 8.4 x 10^4 m/s and has a magnetic force of 3.0 x 10^-18 N east exerted on it. If the magnetic field points upward, what is the magnitude of the magnetic field? (Remember F = qvB)

2.2*10^-4 T

The angle between the first-order maximum and the central maximum for monochromatic light of 2300 nm is 27°. Calculate the number of lines per centimeter on this grating.

2000 lines/cm

Light with a wavelength of 546.1 nm passes through a 6.62 × 10^3 lines/cm diffraction grating. What is the first-order angle of diffraction?

21.2°

A 4.0-W resistor, an 8.0-W resistor, and a 10.0-W resistor are connected in series across an 11-V battery. What value of resistance must be connected in series with the circuit to decrease the current in the circuit by 50.0%?

22 W

An ac generator has a maximum emf output of 150 V. What is the rms current in the circuit when the generator is connected to a 35 W resistor?

3.1 A

An electron moves north at a velocity of 9.8 x 10^4 m/s and has a magnetic force of 5.6 x 10^-18 N west exerted on it. If the magnetic field points upward, what is the magnitude of the magnetic field? (Remember F = qvB)

3.6 x 10^-4 T

How much time is required for 48.96 C of charge to move through an electric juicer if the current through the juicer is 1.39 A?

35.2 s

In the circuit shown below, the battery voltage is 12 volts and the light bulbs are all identical. What is the potential drop across each bulb?

4 volts

Two resistors with values of 6.0 W and 12 W are connected in parallel. This combination is connected in series with a 2.0 W resistor and a 24 V battery. What is the current in the 2.0 W resistor?

4.0

How much current flows through a resistor of 285 ohms if the potential difference across the resistor is 122 volts?

4.28 X 10^-1 A

A 2.0-V battery is connected in a circuit with an ammeter and an unknown resistor, P. The current is observed to be 0.70 A. What would be the current in the circuit if a 12-V battery replaces the 2.0-V battery?

4.2A

A generator with a maximum output emf of 165 V is connected to a 35Ω resistor. Find the maximum AC current in the circuit.

4.7 A

Three resistors of 10.0 W, 20.0 W, and 25.0 W are connected in parallel across a 100-V battery. What is the equivalent resistance of the circuit and the current flowing through the 10.0-W resistor?

5.26 W, 10 A

A potential difference of 115 V across the primary of a step-down transformer provides a potential difference of 2.3 V across the secondary. What is the ratio of the number of turns of wire on the primary to the number of turns on the secondary?

50:1

Light with a wavelength of 400.0 nm passes through a 1.00 × 10^4 lines/cm diffraction grating. What is the second-order angle of diffraction?

53.1°

A 1.5 mF capacitor is connected to a 9.0 V battery. Use the expression PE = 1/2C(DV)^2 to determine how much energy is stored in the capacitor.

6.1 × 10^-5

An AC generator has a maximum output emf of 230 V. The generator is connected to a 25Ω resistor. What is the rms current through the resistor?

6.5A

The distance between the two slits in a double-slit interference experiment is 0.040 mm. The second-order bright fringe (m = 2) is measured on a screen at an angle of 2.2° from the central maximum. What is the wavelength of the light?

770 nm

Two charged particles are separated by a distance of 12 meters. The Coulomb force between them is 20 N. What will the Coulomb force be if the same particles are separated by a distance of 6 meters?

80 N

When a potential difference of 13 V is placed across a resistor, the current in the resistor is 1.4 A. What is the resistance of the resistor?

9.3 Ω

Light with a wavelength of 500.0 nm passes through a 3.39 × 10^5 lines/m diffraction grating. What is the first-order angle of diffraction?

9.73°

The rms emf of an AC generator is 6.9 x 10^2 V. What is the maximum output emf?

9.75 x 10^2 V

A 2.2 resistor has 0.042 A of current in it. What is the potential difference across the resistor?

92 V

A step-down transformer has 2500 turns on its primary and 5.0 × 10^1 turns on its secondary. If the potential difference across the primary is 4850 V, what is the potential difference across the secondary?

97 V

Which statement is correct?

According to the principle of energy conservation, an induced field attempts to keep the total field strength constant.

How is the voltage of the power supply for a series circuit calculated?

Add the voltage of each component in the series.

A laser can be used

All of the above

Which device measures the current in a circuit?

Ammeter

The magnetic force on a straight wire 0.30 m long is 2.6 x 10^-3 N. The current in the wire is 15.0 A. What is the magnitude of the magnetic field that is perpendicular to the wire? (Remember F = BIl)

B=5.8 x 10^-4 T

What is back emf? Does it increase or decrease motor efficiency? Explain.

Back emf is an induced emf in a motor's rotating coil. It decreases motor efficiency, since the back emf reduces the net supply current available in the motor's coil.

Why is a bird able to sit on a power line?

Because both feet are on the same line there is no difference in voltage from foot to foot.

If you hold a magnet up to your refrigerator, why can you feel an attractive force several centimeters away from the surface of the fridge?

Because the magnetic field can extend for a small distance.

Why does the needle of a compass point north?

Because the southern pole of the Earth's magnet is in the north.

What is capacitance?

Capacitance is the measure of the ability of a device to store energy in the form of electrically separated charges.

Which statement is the most correct regarding electric insulators?

Charges within electric insulators do not readily move.

Why is the resolving power for optical telescopes on Earth limited?

Constantly moving layers of air blur the light from objects in space and limit the resolving power.

The electric field strength at the single electron of a hydrogen atom is more than 50 million times the field strength in a lightning bolt. How can you account for this vast difference?

Despite the fact that only one electron is involved, the distances in a hydrogen atom are so small that the field strength is much greater.

What is diffraction?

Diffraction is a change in the direction of a wave when the wave encounters an obstacle, an opening, or an edge.

How does diffraction occur?

Diffraction occurs when waves pass through small openings, around obstacles, or around sharp edges. Wavelets in a wave front interfere with each other to produce light and dark fringes.

An apple contains trillions of charged particles. Why don't two apples repel each other when they are brought together?

Each apple contains equal numbers of positive and negative charges.

Earth's magnetic field shows the correlations between the geographic North Pole and the magnetic South Pole, and the geographic South Pole to the magnetic North Pole.

Earth's magnetic field

What happens when a rubber rod is rubbed with a piece of fur, giving it a negative charge?

Electrons are added to the rod.

If electrons behave like magnets, then why aren't all atoms magnets?

Electrons usually pair up with their spins opposite each other, and their fields cancel each other.

Current passing through a conductor is increased from 10 A to 15 A. This decreases the strength of the magnetic field produced by the conductor.

False

Electric energy is transferred from generating stations to consumers' premises at extremely low voltage.

False

In Earth's magnetic field, the geographic South is also the magnetic South.

False

What happens to the current in the other two lamps if one lamp in a three-lamp parallel circuit burns out?

If one of the filaments burns out, the resistance and the potential difference across the other lamps will not change, therefore their currents will remain the same.

What happens to the current in the other two lamps if one lamp in a three-lamp series circuit burns out?

If one of the lamp filaments burns out, the current will cease and all the lamps will go out.

Which of the following images represents the Coulomb force between two negatively charged particles?

Image D (two particles pointing in opposite directions)

Name the type of emission involved in producing photons in a laser.

In laser, the excited atoms emit the photons by the process of stimulated emission.

While taking his clothes out of the dryer, Charles finds a sock clinging to his sweater. What is the best explanation for this common phenomenon?

In the dryer, either the sock or the sweater gained electrons while the other item lost electrons.

If white light is used instead of monochromatic light to demonstrate interference, how does the interference pattern change?

It becomes blurred, and the bright fringes are made up of narrow, colored bands.

How can the magnetic field around a permanent magnet be determined?

It can be determined with a compass or another magnet that can rotated freely. The direction of the magnetic field is defined as the direction in which the north pole of a compass needle points at that location.

Increasing the potential difference between the plates of a capacitor will produce what effect on the capacitor?

It will increase the charge on each plate.

Fiber-optic systems transmit light by means of internal reflection within thin strands of extremely pure glass. In these fiber-optic systems, laser light is used instead of white light to transmit the signal. Apply your knowledge of refraction to explain why.

Laser light is nearly monochromatic, so it does not spread out very much into different components with different wavelengths as it passes between the fiber and transmission and receiving equipment (that is, dispersion is nearly absent over short distances).

What is 'laser' an acronym for?

Laser stands for 'light amplification by stimulated emission of radiation'.

Explain what happens when you vigorously rub your wool socks on a carpeted floor, touch a metal doorknob, and get a shock.

Loosely held electrons are transferred from the carpet to the socks when the socks are rubbed against the carpet. The body and socks have an excess of electrons and are negatively charged. Touching the doorknob allows the electrons to escape. The shock felt is the sudden movement of charges as the body and socks return to a neutral state.

a group of atoms whose magnetic fields are aligned in a common direction

Magnetic Domain

What is magnetic declination, and where on Earth would the magnetic declination be zero?

Magnetic declination is the difference between true north, which is defined by the axis of rotation of Earth, and north indicated by a compass, which varies from point to point. An imaginary line running north-south near the center of North America currently has zero declination.

All of the following statements about magnetic field lines around a permanent magnet are true except which one?

Magnetic field lines appear to end at the north pole of a magnet.

Why do magnetic poles always occur in pairs?

Magnetic poles cannot be isolated no matter how many times a magnet is cut or subdivided.

What property was discovered in Millikan's experiments? Explain this property.

Millikan discovered that charge is quantized. This means that when any object is charged, the net charge is always a multiple of a fundamental unit of charge. The fundamental unit of charge, which is the charge on the electron, is -1.60×10^-19 C. The charge on a proton is +1.60×10^-19 C.

All of the following are ways to induce an emf in a loop of wire except which one?

Move the loop parallel to a magnetic field.

Explain how the relative motion between a closed circuit and a magnet induces an emf.

Moving charges in a conductor are deflected by the magnetic force of a magnetic field.

Where is a magnetic field strongest?

Near the magnet itself.

A 12- , 2-W resistor is connected in parallel with a 6.0- , 4-W resistor. Which will become hotter if the voltage across them keeps increasing?

Neither. They both reach maximum dissipation at the same voltage.

**R = V/I, where R = resistance, V = voltage, and I = current

Ohm's Law

What happens to the polarity of an electromagnet when the direction of the current passing through it is reversed?

On reversing the direction of the current through an electromagnet, its polarity is also reversed.

The display on this gizmo is a virtual ______.

Oscilloscope

Two particles are 15 meters apart. Particle A has a charge of 6.0 • 10^−4 C, and particle B has a charge of 5.0 • 10^−4 C. The resulting Coulomb force is 12 N. At the same distance, what combination of charges would yield the same Coulomb force?

Particle A: 12.0 • 10^−4 C, and particle B: 2.5 • 10^−4 C

How can you direct the fired proton's path downward?

Place a proton above the original path

What formula is used to calculate resistance using the color code?

R = (First digit * 10 + second digit) * multiplier.

Which waves in the electromagnetic spectrum have the longest wavelength? Which waves have the shortest wavelength?

Radio waves have the longest wavelength in the electromagnetic spectrum. Gamma rays have the shortest wavelength.

There is a 0.40-A current in resistor X when it is connected to a 2.0-V battery. A 0.25-A current is in a second resistor, Y, when it is connected to a 4-V battery. There is a 0.50-A current in a third resistor, Z, when it is connected to a 5.0-V battery. Find the resistor that has the maximum resistance and the resistor that has the least resistance.

Resistor Y has the maximum resistance, while resistor X has the least resistance.

A unit of magnetic induction equal to one weber per square meter; measures magnetic field strength based on force, charge and speed.

Tesla

What unit is used to describe the magnitude of a magnetic field? What does this unit represent?

The Tesla is the unit that is used to describe the magnitude of a magnetic field. It represents N/(C per m/s).

Why is the energy produced by an alternating current with a maximum value of not the same as that produced by a direct current with the same value?

The alternating current is at its maximum value for only an instant during its cycle.

What is the alternative right-hand rule used for?

The alternative right-hand rule is used to find the direction that a magnetic force will travel through a magnetic field.

What is the SI unit for current?

The ampere (A) is the SI unit for current.

The spacing between the plates of a particular capacitor is reduced from 1.5 × 10^-2 cm to 1.5 × 10^-5 cm. How will this spacing change affect the capacitor?

The capacitance of the capacitor will increase to 1000 times its original value.

How does an electromagnetic wave propagate itself?

The changing electric field induces a magnetic field perpendicular to the electric field. The induced magnetic field then induces another electric field, and so forth.

Two unknown charges are shown in the diagram. Using your knowledge of force lines, predict which charge is positive and which is negative.

The charge on X is positive (force lines point away from the charge) and the charge on Y is negative (force lines point toward the charge).

On a separate sheet of paper, draw the lines of force representing the electric field surrounding two objects that have equal magnitude charges of opposite polarity. Describe these lines in the space provided.

The electric field lines move in a circular fashion away from the positive charge and towards the negative charge.

If the head of an iron nail touches a magnet, the nail will become magnetized. If the nail touches the north pole of the magnet, what kind of pole is at the head of the nail? Explain.

The end of the magnetized nail touching the north pole of the magnet must be a south pole. Otherwise, the magnet would repel the nail.

Explain how the terms energy, electromagnetic force, electromagnetic wave, and electromagnetic radiation are related to one another.

The energy of an electromagnetic wave is stored in the electromagnetic fields, which exert an electromagnetic force on charged particles. This energy transported by an electromagnetic wave is called electromagnetic radiation.

***What occurs when two charges are moved closer together?

The force between the charges increases.

In the series circuit shown below, if one of the light bulbs were removed from the circuit, what would happen to the remaining light bulbs? (Assume that the circuit remains the same in all other ways.)

The lights would go out.

In the parallel circuit shown below, if one of the light bulbs were removed from the circuit, what would happen to the remaining light bulbs? (Assume that the circuit remains the same in all other ways.)

The lights would shine with the same brightness.

Why are iron cores or rods used in solenoids that act as electromagnets?

The magnetic field of the solenoid creates a temporary magnetic field in the iron core. This increases the magnetic field of the electromagnet.

Which magnetic pole is at the geographic South Pole of Earth?

The magnetic north pole is located at the geographic South Pole of Earth.

Which magnetic pole is at the geographic North Pole of Earth?

The magnetic south pole is located at the geographic North Pole of Earth.

Suppose you have one magnet in a straw with its South pole pointed upward. What would happen if you put another magnet into the straw with its North pole pointed downward?

The magnets would be attracted to each other.

Suppose you have one magnet in a straw with its North pole pointed upward. What would happen if you put another magnet into the straw with its North pole pointed downward?

The magnets would repel each other.

Where is the magnitude of the magnetic field around a permanent magnet greatest?

The magnitude is greatest close to the poles.

How is the magnitude of a magnetic field calculated?

The magnitude of a magnetic field is calculated using the following equation: B = F/qv, where B is the magnetic field magnitude, F is the magnetic force, q is the charge of the particle, and v is the velocity of the particle.

Move object A back and forth. How does the distance between the objects affect the strength of the electrostatic force between them?

The magnitude of the electrostatic force decreases as the objects move apart.

Describe the pattern that results from the single-slit diffraction of monochromatic light.

The pattern is one of alternating light and dark bands. The brightest light band is at the center and is twice as wide as the other bands. The light bands decrease in brightness as the distance from the center increases.

What is potential difference?

The potential difference is the change in the electrical potential energy associated with a charged particle divided by the charge of the particle.

The operating voltage of a power line is increased from 300 kV to 600 kV. If the amount of power delivered to customers over the power line remains constant, how does the power loss in the power line at 300 kV compare to the power loss at 600 kV? Explain.

The power loss at 300 kV is four times the loss at 600 kV. To deliver the same amount of power, the current in the 300 kV line is twice the current in the 600 kV line. The power loss is proportional to the square of the current through the line.

A device having a constant resistance operates at a voltage of 100 V. If the voltage supplied to the device increases by 10 percent, how does this affect the power used by the device relative to the power consumption at 100 V?

The power used by the device increases to 120 percent of its power consumption at 100 V.

What happens when a proton is fired without any positive or negative forces within the grid?

The proton will pass straight through the grid without changing its path

In a primary-secondary coil combination, which of the following conditions is met in the primary coil when the current in the secondary coil is at its maximum?

The rate of current change is maximum.

Two parallel conducting wires are placed side by side. Each is carrying a current, and the currents are traveling in opposite directions. Will these wires attract or repel each other?

The wires will repel each other.

A rubber rod can be charged negatively when it is rubbed with wool. What happens to the charge of the wool?

The wool becomes positively charged.

What value must be known to determine the current in a complex circuit?

To determine the current, the equivalent resistance of the circuit must be known.

A wire in a lamp that is turned on would have a magnetic field around it.

True

Which of the following situations is not true for magnets?

Unlike poles repel each other.

How does light from a laser differ from light whose waves all have the same wavelength but are not coherent?

Waves emitted by a laser do not shift relative to each other as time progresses (they are coherent and continuously in phase).

Which of the following materials is the best conductor of electricity?

Wet skin

Thoroughly describe the magnetic field characteristics as an induced current is produced in a coil of wire by an approaching and receding magnet.

When an applied magnetic field approaches the coil of wire, the direction of the induced current produces an induced magnetic field that is in a direction opposite the approaching (or strengthening) magnetic field. As a result, these magnetic fields repel each other. When the applied magnetic field moves away from the coil of wire, the direction of the induced current once again produces a magnetic field that is in a direction opposite the receding (or weakening) magnetic field. This time, however, the induced magnetic field is in the same direction as the receding magnetic field. As a result, these magnetic fields attract each other.

What happens when the like poles of two magnets are placed next to each other?What happens when the unlike poles of two magnets are placed next to each other?

When like poles are placed next to each other, the magnets repel each other. When unlike poles are placed next to each other, the magnets attract each other.

Why is it frustrating when one bulb burns out on a string of holiday tree lights connected in series?

When one bulb burns out, the circuit is opened and all of the bulbs go out.

Is it possible to orient a current-carrying loop of wire in a uniform magnetic field so that the loop will not tend to rotate?

Yes, by aligning the plane of the loop perpendicular to the magnetic field.

Why are current and resistance kept very low?

[NOT] c. Both a and b.

How can you increase the strength of a magnetic field inside a solenoid?

[NOT] increase the number of coils per unit length

What is the function of a transformer at a power station?

[NOT] none of the above

A conductor carrying a current is arranged so that electrons flow in one segment from east to west. In what direction is the magnetic field moving? (Hint: Recall that current is defined as the motion of positive charges.)

[NOT] north

A 10.0 ohm resistor, 20.0 ohm resistor, and a 25.0 ohm resistor are connected in series across a 110-V supply. Calculate the current in the circuit.

a. 2.0 A

The distance between two charges q_a and q_b is r, and the force between them is F. What is the force between them if the distance between them is doubled?

a. F/4

How is current affected if the time interval over which the charge passes through a given area decreases while the amount of charge remains the same?

a. The current increases.

The power ratings on lightbulbs are measures of the

a. rate that they give off heat and light.

What is the path of an electron moving parallel to a uniform magnetic field?

a. straight line

Which of the following is NOT a way lasers are used in medicine?

all are uses of lasers in medicine

Which of the following options can be used to generate electricity?

all of the above

Which of the following statements about electromagnetic radiation is true?

all of the above

Measures the current in a branch or part of a circuit

ammeter

A flow of electric charge, or electric current, equal to one coulomb per second (1C/s).

ampere

An electromagnetic wave is produced by:

an accelerating charged particle or changing magnetic fields

Which of the following is not a characteristic of electrical potential energy?

b. It results from a single charge.

What do radio waves, microwaves, X rays, and gamma rays all have in common?

b. They are electromagnetic waves.

The ratio of an object's stored charge to its electric potential difference.

capacitance

The SI standard unit of charge; one coulomb, C, is the magnitude of the charge of 6.24x1018 electrons or protons.

coulomb

Under which of the following conditions is the net magnetic force on a charged particle equal to zero?

d. all of the above

Where is the electric field of an isolated, uniformly charged, hollow metallic sphere greatest?

d. at the sphere's outer surface

When compared in a given time interval with other lightbulbs connected to a 120 V circuit, a 60 W lightbulb

d. converts less electrical energy to heat and light than a 100 W lightbulb.

In a permanent magnet,

domain alignment persists after the external magnetic field is removed.

A closed loop or pathway that allows electric charges to flow.

electric circuit

What kind of energy conversion occurs in a motor?

electrical energy to mechanical energy

List three essential components of an ac generator.

field magnet, slip rings, and brushes

If two lightbulbs are placed side by side, no interference is observed because

incandescent light is incoherent.

A current due to variation in the magnetic field surrounding its conductor.

induced current

Conductors can be charged by ____, while insulators cannot.

induction

The total magnetic induction crossing a surface, equal to the integral of the component of magnetic induction perpendicular to the surface over the surface: usually measured in webers or maxwells.

magnetic flux

Which conversion process is the basic function of the electric generator?

mechanical energy to electrical energy

How many electromagnetic forces exist?

one

The value of an ac circuit that gives the same heating effect as a corresponding dc value

rms value

An attracting force occurs between two charged objects when the charges are of

unlike signs

If the work done in moving a charge is doubled and the strength of the charge is halved, the electric potential difference:

increase to four times its original value

When a comb is run though your hair and brought near a small piece of paper, the paper is attracted to the comb due to

induction

A material through which a charge does not move easily

insulator

A material, such as glass, through which a charge will not move easily.

insulator

Materials, such as glass, in which electric charges do not move freely are called electrical ____________________.

insulators

A helium-neon laser shines monochromatic light (l = 632.8 nm) perpendicular to the surface of a diffraction grating that contains 146 230 lines/m. Find the angles at which one would observe the second-order and third-order maxima.

q_1 = 10.66°; q_2 = 16.11°

A diffraction grating that contains 650 472 lines/m is illuminated by monochromatic light (l = 632.8 nm) from a helium-neon laser directed perpendicular to the surface of the grating. At what angles would one observe the first-order and second-order maxima?

q_1 = 24.30°; q_2 = 55.38°

Mutual inductance, M, is dependent on what two factors?

the geometrical properties of the coils and their orientation to each other

According to Lenz's law, if the applied magnetic field changes,

the induced field attempts to keep the total field strength constant.

According to the right-hand rule, if a current-carrying wire is grasped in the right hand with the thumb in the direction of the current, the four fingers will curl in the direction of

the magnetic field, B

What does the minus sign in front of Faraday's law of magnetic induction indicate? How does it relate to Lenz's law?

the polarity of the induced emf; The induced magnetic field opposes the change in the applied magnetic field as stated by Lenz's law.

Which set of information will allow you to calculate the kilowatt•hr usage?

the resistance, the current, and the time the circuit operates

If the potential difference across an outlet is measured at 220 V, what circuit value is actually being measured?

the rms emf (or rms potential difference)

Consider two long, straight, parallel wires, each carrying a current I. If the currents move in the same direction,

the two wires will attract each other

Consider two long, straight, parallel wires, each carrying a current I. If the currents move in opposite directions,

the two wires will repel each other.

Name four factors that affect the magnitude of the induced emf in a closed loop of wire.

the velocity of the wire through the magnetic field, the length of wire, the magnetic field strength, the angle between the magnetic field and the wire

What property does the electromagnetic force share with gravity, light, and sound?

their magnitudes obey the inverse-square law

If light waves are coherent,

they remain in phase.

What is a turbine's rotational motion used for in commercial power plants?

to turn wire loops (or a coil of wire) in a magnetic field

A device that increases or decreases the emf of alternating current.

transformer

What extremely useful device is based on the principle of mutual inductance?

transformer

What does an ac transformer consist of in its simplest form?

two coils of wire wound around a core of soft iron

A generator consists of 10.0 turns of wire, and each turn has an area of 0.095m^2 If a maximum emf of 1.5 x 10^2V is induced when the coil rotates with a frequency of 60.0 Hz, what is the strength of the magnetic field? Hint: Remember the equation ω = 2πf from previous lesson.

b. 0.34 T

A positive charge of 3.50 µC is located in an electric field of intensity 3.00 N/C directed toward the south. Find the magnitude and the direction of the force on the test charge.

b. 1.05 x 10^-5 toward the south

The amount of charge that moves through the filament of a lightbulb in 2.00 s is 2.67 C. What is the current in the lightbulb?

b. 1.33 A

A student makes a voltage divider from a 45-V battery, a 475-ohm resistor, and a 235-ohm resistor. When the output is measured across the smaller resistor, what voltage is shown?

b. 15 V

A 0.25 mF capacitor is connected to a 9.0 V battery. What is the charge on the capacitor?

b. 2.2×10−6 C

A sphere with a charge of 1.5 x 10^-6 C experiences a force of 3.5 x 10^2 N when it is located at a certain point in an electric field. Determine the magnitude of the electric field intensity at this location.

2.3 x 10^8 N/C

How far from a point charge of +2.4 x 10^-6 C must a test charge be placed to measure a field of 360 N/C?

b. 7.7 m

Which way will the force lines point in a diagram of the electric field surrounding a positive charge?

b. Away from the charge

The units for expressing electric field strength include:

b. Newtons/Coulombs

If a resistor is added to a parallel circuit, the equivalent resistance:

b. decreases

Which process will double the power dissipated by a resistor?

b. doubling the current and making the resistance half as big

Which conversion process is the basic function of the electric motor?

b. electrical energy to mechanical energy

***In any complex resistance circuit, the voltage across any resistor in the circuit is always

b. equal to or less than the voltage source.

Where is energy stored in electromagnetic waves?

b. in the oscillating electric and magnetic fields

A double-slit interference experiment is performed using blue light with a wavelength of 486 nm. The fifth-order bright fringe in the interference pattern is 0.578º from the central maximum. What is the distance between the two slits?

2.41 x 10^-4 m

An AC generator has a maximum output emf of 4.20 x 10^2 V. What is the rms emf?

297 V

What would the resistance be of a series circuit containing a 10 ohm resistor, a 20 ohm resistor, and a 10 volt battery?

30 ohms

A generator supplies an rms current of 9.50 A. If the resistance of the circuit is 24.0 Ω, what is the maximum emf?

322 V

The process of charging a conductor by bringing it near another charged object and then grounding the conductor is called

b. induction.

If a positively charged glass rod is used to charge a metal bar by induction, the charge on the bar

b. must be negative.

What are some applications of electric current?

Electric current powers lights and home appliances. It also ignites the gasoline in automobile engines, and it is used in microcomputers.

How are gravitational force and electric force different?

Electric force is stronger than gravitational force. Also, electric force can be attractive or repulsive, but gravitational force is always attractive.

What is electric power?

Electric power is the rate at which charge carriers convert electric potential energy to other forms of energy.

What is the difference between an electrical conductor and an electrical insulator?

Electrical conductors have electric charges that move freely, while the charges within electrical insulators do not readily move.

Which sentence best describes electrical conductors?

Electrical conductors have electric charges that move freely.

Describe electromagnetic waves.

Electromagnetic waves are made of electric and magnetic fields that are oscillating at right angles to each other and to the direction of wave motion.

A bar magnet is suspended and allowed to rotate freely. If the magnetic field of Earth is considered to be similar to that of a large bar magnet, which pole of the suspended magnet would point toward the magnetic north pole of Earth?

b. the south pole

The emf induced in a motor's coil that tends to reduce the current in the coil of the motor.

back emf

A magnet in the form of a bar with magnetic poles at each end.

bar magnet

A device made up of several galvanic cells connected together that converts chemical energy to electric energy.

battery

Why is power lost in real transformers?

because of small currents induced by changing magnetic fields in the transformer's iron core and because of resistance in the wires

A steam turbine at an electric power plant delivers 4500 kW of power to an electrical generator that converts 95 percent of this mechanical energy into electrical energy. What is the current delivered by the generator if it delivers energy at 3600 V?

c. 1.2×10^3 A

The current in an electron beam in a cathode-ray tube is 7.0 × 10^-5 A. How much charge hits the screen in 5.0 s?

c. 3.5×10^−4 C

A 4.0-ohm resistor, an 8.0-ohm resistor, and a 10.0-ohm resistor are connected in series across an 11-V battery. The total voltage drop across the 4.0-ohm and 8.0-ohm resistors is:

c. 6.0 V

If the charge is tripled for two identical charges maintained at a constant separation, the electric force between them will be changed by what factor?

c. 9

If a 325 W heater has a current of 6.0 A, what is the resistance of the heating element?

c. 9.0Ω

Which of the following statements is true about electric forces?

c. Electric forces cause objects to repel or attract each other.

What happens to the capacitance if the charge on the plates of a capacitor is doubled?

c. The capacitance remains unchanged.

If a proton is released at the equator and falls toward Earth under the influence of gravity, the magnetic force on the proton will be toward the ____ assuming the magnetic field is directed toward the north at this location.

c. east

When a charged body is brought close to an uncharged body without touching it, a(n) ____ charge may result on the uncharged body. When a charged body is brought into contact with an uncharged body and then is removed, a(n) ____ charge may result on the uncharged body.

c. induced; residual

An electric device used to store charge that is made up of two conductors separated by an insulator.

capacitor

Which of the following elements is NOT magnetized temporarily in the presence of a permanent magnet?

carbon

When an iron rod is inserted into a solenoid coil's center, the magnetic field produced by the current in the loops

causes alignment of the domains in the iron.

Electric field strength depends on

charge and distance

The process of charging a neutral object by touching it with a charged object.

charging by conduction

The process of charging an object without touching it, which can be accomplished by bringing a charged object close to a neutral object, causing a separation of charges, then separating the object to be charged, trapping opposite but equal charges.

charging by induction

***An automatic switch that opens when the current reaches a set value is called:

circuit breaker

An automatic switch that acts as a safety device in an electric circuit by opening and stopping the current flow when too much current flows through a circuit.

circuit breaker

Two parallel conducting wires are placed side by side. Each is carrying a current, and the currents are traveling in the same direction. Will these wires attract or repel each other?

The wires will attract each other.

Explain why there is no induced current in a closed loop of wire when the area of the loop is perpendicular to the magnetic field.

When the area of the loop is perpendicular to the magnetic field, every segment of the wire in the loop is moving parallel to the magnetic field. At this point, no magnetic field lines are being crossed. Consequently, there is no magnetic force on any of the charges in the wire segments.

When does constructive interference occur in the gizmo?

When the lines of one circle line up with the lines of the other

When does destructive interference occur in the gizmo?

When the lines of one circle line up with the spaces of the other

If a solenoid were suspended by a string so that it could rotate freely, could it be used as a compass when it carried a direct current? Could it also be used if the current were alternating in direction?

Yes, the north pole of the solenoid would point to Earth's geographic North Pole; No, the solenoid would oscillate back and forth as its poles continually reversed.

Did Young discover that coherent light behaves the same way as two point sources producing circular waves in a ripple tank in his double slit interference experiment?

Yes.

The distance between two slits in a double-slit interference experiment is 2.9 × 10^-6 m. The first-order bright fringe is measured on a screen at an angle of 12° from the central maximum. What is the wavelength of the light?

[NOT] 3.0 × 10^2 nm

An electron moves across Earth's equator at a speed of 2.5 × 10^6 m/s and in a direction 35° north of east. At this point, Earth's magnetic field has a direction due north, is parallel to the surface, and has a value of 0.10 × 10^-4 T. What is the magnitude of the force acting on the electron due to its interaction with Earth's magnetic field?

[NOT] 3.3 × 10^-18 N

Two slits are spaced 0.33mm apart. If the angle between the first dark fringe and the central maximum is 0.055º, what is the wavelength of a light falling on these two slits?

[NOT] 540 nm

A current can be induced in a closed circuit without the use of a battery or an electrical power supply by moving the circuit through a

[NOT] high temperature field

What induces a current in the secondary coil of a two-coil system?

a changing current in the primary coil

What device produces an intense, nearly parallel beam of coherent light?

a laser

Which of the following correctly describes the composition of an electromagnetic wave?

a transverse electric wave and a magnetic transverse wave that are perpendicular and are moving in the same direction

A bulb is connected to a 12-V battery and a current of 0.3 A is measured in the bulb. A.Calculate the resistance of the bulb. B. If the bulb is connected to a 24-V battery, the current is measured to be 0.50 A. What is the resistance of the bulb?

a-40 Ohms, b-48 Ohms

How much does it cost to operate a 695 W heater for exactly 30.0 min if electrical energy costs $0.060 per kW·h?

a. $0.02

A 22-ohm resistor and a 33-ohm resistor are connected in series and placed across a 120-V potential difference. What is the current in the circuit?

a. 2.2 A

A transformer has 15 turns in its primary and 6750 turns in its secondary. If the potential difference across the primary is 1.2 V, what is the potential difference across the secondary?

a. 540 V

A 4.7 x 10 resistor has a current of 1.27 x 10^-1 A flowing in it. What is the potential difference across the resistor?

a. 6.0 V

A long, straight, current-carrying wire runs from north to south. If you know the direction of the current, how can you determine the direction of the magnetic field?

a. Grasp the wire in your right hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.

George inserts a long straight wire running from south to north in a circuit. The direction of the conventional current is also from south to north./ a-What is the direction of magnetic field of this current-carrying wire?/ b-What happens to the direction of magnetic field if the direction of flow of the conventional current is reversed?/ c-Name the rule used in solving parts a and b of this question.

a. If the direction of the current is from south to north, then the direction of magnetic field is counterclockwise around the wire. b. If the direction of the conventional current is from north to south, the magnetic field reverses its direction and is clockwise around the wire. c. The first right-hand rule has been used in solving parts a and b.

A generator with a single loop produces the greatest magnetic force on the charges and the greatest induced emf when

a. the plane of the loop is parallel to the magnetic field

The relative distribution of charge density on the surface of a conducting solid depends upon which of the following?

a. the shape of the conductor

____________ are used to calculate the distance a continent has moved in a year.

all of the above

An electric current that changes direction at regular intervals.

alternating current

An electric current that changes directions at regular intervals is called

alternating current

The alternative right hand rule is a method used to determine the direction of the magnetic force on a positive charge.

alternative right hand rule

A low resistance device connected in series that is used to measure the electric current in any branch or part of a circuit.

ammeter

The correlation between the phases of two or more waves.

coherence

Light in which the electromagnetic waves maintain a fixed and predictable phase relationship with each other over a period of time.

coherent light

A complex electric circuit that includes both series and parallel branches.

combination series-parallel circuit

___________ charges a neutral body by touching it with a charged body.

conductance

A substance or medium that conducts heat, light, sound, or especially an electric charge.

conductor

Charge is most easily transferred in

conductors.

Electric charge is

conserved.

For stable interference to occur, the phase difference must be

constant.

The light regions are areas of __________ interference.

constructive

A superposition of two or more waves in which individual displacements on the same side of the equilibrium position are added together to form the resultant wave.

constructive interference

The bright lines in a double-slit interference pattern are due to _______.

constructive interference

A flow of positive charges that move from higher potential to lower potential.

conventional current

Calculated in a series circuit by the equation I = V/R

current

In a series circuit, each circuit element has the same:

current

Lenz's law states that the magnetic field of the induced ____________________ is in a direction to produce a field that ____________________ the change causing it.

current, opposes

A short piece of metal that acts as a safety device in an electric circuit by melting and stopping the current from flowing if a dangerously high current passes through the circuit.

fuse

A short piece of metal that melts when a large current passes through it is a:

fuse

Name three common safety devices associated with household wiring.

fuses, circuit breakers, ground-fault interrupters

A device that is used to measure very small currents; can be used as a voltmeter or an ammeter.

galvanometer

A machine that converts mechanical energy into electrical energy.

generator

A device that contains an electronic circuit that detects small current differences caused by an extra current path; it opens the circuit, prevents electrocution and often is required as a safety measure for bathroom, kitchen, and exterior outlets.

ground-fault interrupter

The process of removing excess charge by touching an object to Earth.

grounding

Lasers produce beams from light waves that are __________.

high amplitude

The light emitted from a substance or object as a result of heating it to a high temperature; produced by glowing light sources such as candle flames, light bulbs and the Sun.

incandescent light

Light with unsynchronized wave fronts that illuminates objects with an even, white light.

incoherent light

Electromagnetic waves are ____ electric and magnetic fields.

oscillating

A type of electric circuit in which there are several current paths; its total current is equal to the sum of the currents in the individual branches, and if any branch is opened, the current in the other branches remains unchanged.

parallel circuit

A type of connection in which the circuit component and the voltmeter are aligned parallel to one another in the circuit, the potential difference across the voltmeter equals the potential difference across the circuit, and there are two or more paths.

parallel connection

The difference in the distance traveled by two beams when they are scattered in the same direction from different points.

path difference

The direction of the force on a current-carrying wire in an external magnetic field is

perpendicular to both the current and to the magnetic field

Coherence is the property by which two waves with identical wavelengths maintain a constant

phase relationship.

A unit or quantum of light; a particle of electromagnetic radiation that has zero mass and carries a quantum of energy.

photon

Is the charge shown in the figure above positive or negative?

positive

When an object loses electrons, it acquires a(n) ____________________ electric charge.

positive

A large conducting sphere with a large net negative charge is brought close to but does not touch a small, uncharged conducting small sphere. A wire connects the small sphere to a metal plate. If the wire to the metal plate is disconnected and the large sphere is removed, what are the charges on the smaller sphere and on the metal plate?

positive on the small sphere and negative on the plate

What is electrical potential energy?

potential energy associated with a charge due to the position of the charge in an electric field

A quantity that measures the rate at which work is done or energy is transformed.

power

Equal to current multiplied by electric potential difference

power

The atomic particle that has a charge opposite to that of an electron is called a(n) ____________________.

proton

The acronym laser stands for light amplification by ____ emission of radiation.

stimulated

What property of lasers causes coherent light to be emitted?

stimulated emission

What determines the frequency of an electromagnetic wave?

the frequency of oscillation or the wavelength

What is the value of charge of a body that carries 20 excess electrons?

-3.20*10^-18 C

A coil with a wire is wrapped 40.0 turns around a 0.50m^2 hollow tube. A magnetic field is applied perpendicularly to the plane of the coil. The field changes uniformly from 0.00 T to 0.95 T in 2.0 s. If the resistance in the coil is 3.0Ω, what is the magnitude of the induced current?

-3.2A

A coil with 150 turns and a cross-sectional area of 1.00m^2 experiences a magnetic field whose strength increases by +0.65T in 1.80 s. The plane of the coil is perpendicular to the plane of the applied magnetic field. What is the induced emf in the coil?

-54 V

The maximum current supplied by a generator to a 25 ohm circuit is 6.2 A. What is the rms potential difference?

110 V

What is the total resistance of the circuit shown below?

12 ohms

What would the resistance be of a series circuit containing a 100 ohm resistor, a 20 ohm resistor, and a 15 volt battery?

120 ohms

A coil with 25 turns of wire moves through a uniform magnetic field of 1.5 T. The plane of the magnetic field is perpendicular to the plane of the coil. The coil has a cross-sectional area of 0.80m^2. The coil enters and exits the field over 1.0 s. If the coil's resistance is 2.0Ω, what is the induced current?

15 A

What is electric current?

Electric current is the rate at which electric charges move through an area.

One kilowatt-hour is equal to the energy consumed by an electric device of 1 W for 1 hour.

False

The charge shown in the figure is positive.

False

The strength of an electric field around a charged object is equal to the force on a positive test charge multiplied by the strength of the test charge.

False

Faraday's Law of Induction is used to determine the magnitude of the induced emf in a circuit.

Faraday's Law of Induction

Which of the lasers in the table above emits the reddest light (visible light with the longest wavelength)?

GaAlAs

A device that detects small current differences and prevents electrocution that is often required as a safety measure for bathroom, kitchen, and exterior outlets.

Ground-fault interrupter

The distance between two slits in a double-slit interference experiment is 0.0050 mm. What is the angle of the third-order bright fringe (m = 3) produced with light of 550 nm?

19°

An electron moves north at a velocity of 6.2 x 10^6 m/s and has a magnetic force of 2.1 x 10^-18 N exerted on it. If the magnetic field points upward, what is the magnitude of the magnetic field? (Remember F = qvB)

2.1 x 10^-6 T

***Heating this will convert electrical energy to thermal energy

...

What would the current be in a series circuit containing a 200 ohm resistor, a 20 ohm resistor, and a 10 V battery?

0.05 amperes

If it takes 15 minutes to dry your hair with a 1.200 kW hair drier, how much energy is used in drying your hair?

0.300 kWh

In the circuit shown below, the battery voltage is 20 volts and the resistors have values of 20 ohms and 30 ohms. What will be the reading of the ammeter shown in the circuit? Hint: V = I x Total R

0.40 amperes

A coil with 650 turns produces an emf of 120 V as it passes through a magnetic field in 2.7 s. The magnetic field change is -0.935 T. The plane of the coil moves perpendicularly to the plane of the magnetic field. What is the area of the coil?

0.53 m^2

A current-carrying wire 0.50 m long is positioned perpendicular to a uniform magnetic field. If the current is 10.0 A and there is a resultant force of 3.0 N on the wire due to the interaction of the current and field, what is the magnetic field strength?

0.60 T

A 120.0 resistor, a 60.0 resistor, and a 40.0 resistor are connected in parallel and placed across a 12.0-V battery. What is the current of the entire circuit?

0.600 A

What is the angle between the first-order and second-order bright fringes for a yellow light with a wavelength of 605 nm, and a distance between two slits of 0.0550 mm?

0.630º

An ac generator has a maximum output emf of 120 volts. The generator is connected to a 125 ohm resistor. What is the rms current through the resistor?

0.68 A

A wire 48 m long carries a current of 18 A from west to east. If a magnetic field of 8.3 x 10^-4 T directed toward the south is acting on the wire, find the direction and magnitude of the magnetic force.

0.72 N downward

If two light waves are in phase, what is the smallest amount by which their phases can differ?

0°

A coil with 6.00 x 10^2 turns and a cross-sectional area of 1.50m^2 experiences a magnetic field for 6.00 s. The plane of the coil is perpendicular to the plane of the magnetic field. The magnetic field changes from 0.450 T to -0.300 T. What is the induced emf in the coil?

1.13 x 10^2 V

A 2.00-W resistor and a 12.0-W resistor are connected in parallel across a 20.0-V battery. What is the current flowing through the 2.00-W resistor?

10.0 A

A helium-neon laser placed perpendicular to a diffraction grating that contains 149 638 lines/m illuminates the grating's surface with monochromatic light with a wavelength of 632.8 nm. At what angle will the second-order maximum appear?

10.9°

Monochromatic light from a helium-neon laser (l = 632.8 nm) shines at a right angle onto the surface of a diffraction grating that contains 130 960 lines/m. Find the angle at which one would observe the first-order maximum.

4.752°

Four resistors of 10.0 W each are connected in parallel. A combination of four resistors of 10.0 W each is connected in series along with the parallel arrangement. What is the equivalent resistance of the circuit?

42.5

A power drill runs at a voltage of 120 V and draws a current of 4 A. What is the wattage of the drill?

480 W

The distance between the two slits in a double-slit experiment is 0.0025 mm. The third-order bright fringe (m = 3) is measured on a screen at an angle of 35° from the central maximum. What is the wavelength of the light?

480 nm (4.8*10^2 nm)

A parallel-plate capacitor has a capacitance of C F. If the area of the plates is doubled while the distance between the plates is halved, the new capacitance will be

4C

Monochromatic light shines on the surface of a diffraction grating with 5.3 × 10^3 lines/cm. The first-order maximum is observed at an angle of 17°. Find the wavelength.

550 nm

The distance between two slits in a double-slit experiment is 4.2 X 10^-6m. The first-order bright fringe is measured on a screen at an angle of 8.0° from the central maximum. What is the wavelength of the light?

580 nm

What is the force between two small charged spheres that have charges of 2 x 10-7 C and 3 x 10-7 C and are placed 30 cm apart in air?

6*10^-3 N

Three 20-ohm resistors are connected in series across a 120-V generator. Find the equivalent resistance of the circuit.

60Ω

What are the advantages of using a "laser knife" in surgical procedures?

A "laser knife" cuts through tissue like a steel scalpel; however, the energy from the laser coagulates blood, sealing the blood vessels and preventing blood loss and infection.

What is true about an electric motor?

A and B

What is the function of a transformer?

A and B are correct.

What type of path will a charge moving through a magnetic field follow? Where will the magnetic force be directed in this path?

A charge moving through a magnetic field will follow a circular path. The magnetic force will always be directed toward the center of the circular path.

What is the function of a fuse? What is the function of a circuit breaker?

A fuse is a short piece of metal that melts when a large current passes through it. A circuit breaker is a switch that automatically opens when the electrical current traveling to it reaches a set value.

A voltmeter is used to measure the voltage across a device and is placed in parallel with the device. All voltmeters have resistance. Why would a voltmeter with a high resistance be preferable to one with low resistance when measuring the voltage across a resistor that is part of a complex circuit?

A high-resistance voltmeter would not alter the resistance of the circuit as much as a voltmeter with a lower resistance. Because the resistance of the voltmeter is in parallel with the resistor across which the voltage is being measured, a high-resistance voltmeter will give a more accurate voltage reading than a voltmeter with a lower resistance.

What pattern is generated with all X parameters are at their maximum and all Y parameters are at their minimum?

A horizontal line

If the X and Y values for each parameter are equal, what does the readout look like?

A line

What is a magnetic domain?

A magnetic domain is a group of neighboring atoms containing electrons with their magnetic fields aligned in the same direction.

What is a short circuit? Why is a short circuit dangerous?

A short circuit is a circuit that has extremely low resistance. A short circuit is dangerous across any potential difference because it will produce a large current. The heating effect of the current can cause a fire.

What is the function of a spectrometer?

A spectrometer separates light from a source into its monochromatic components.

Why does a car's ignition system need a transformer to work? What kind of transformer is in a car's ignition system?

A transformer is needed to convert a car battery's 12 dc volts to a larger potential difference so sparking will occur in the spark plug gaps and ignite the fuel. It is a step-up transformer.

Use the magnetic domain model to compare and contrast hard and soft magnetic materials.

According to the magnetic domain model, both hard and soft magnetic materials have groups of neighboring atoms whose magnetic fields are aligned. Soft magnetic materials tend to gain or lose their domain alignments easily, depending on whether or not a the material is immersed in a magnetic field. Hard magnetic materials retain their domain alignments whether or not they are immersed in a magnetic field. As a result, soft magnetic materials are easily magnetized, but also lose their magnetism easily. Hard magnetic materials are difficult to magnetize, but keep their magnetism for long periods of time.

One useful way to model magnetic field strength is to define a quantity called magnetic flux . Which of the following definitions for magnetic flux, , is correct?

All of the above

How does the way in which an ammeter is connected in a circuit differ from the way in which a voltmeter is connected?

An ammeter is connected in series; a voltmeter is connected in parallel.

What is the function of an ammeter?

An ammeter measures the current in a circuit.

Which of the following devices would you expect to consume the most energy for each hour that it operates?

An electric space heater

Why is household wiring constructed in parallel instead of in series?

Appliances in parallel can be run independently of one another.

Why does a generator produce a continuously changing emf?

As the loop rotates, the direction and number of wire segments that cross the magnetic field lines are constantly changing.

How are lasers used to determine the distance from Earth to the moon?

Astronomers direct a pulse of light toward one of several reflectors that were placed on the moon's surface by astronauts. The distance from Earth to the moon can be measured by finding the time the light takes to travel to the moon and back.

An operating (turned on) lightbulb has a resistance that is about 10 to 20 times greater than when it is not operating (turned off). How does this explain why lightbulbs often burn out at the moment they are turned on?

At the instant the bulb is turned on, the lower resistance results in a current through the bulb that is 10 to 20 times greater than the operating current. This high current may cause physical damage to the filament in the lightbulb.

In the diagram shown above, the circles represent small balls that have electric charges. Ball 1 has a negative charge, and ball 2 is repelled by ball 1. Next, you see that ball 2 repels ball 3 and that ball 3 attracts ball 4. What is the electric charge on ball 4?

Ball 4 has a positive charge.

When the two circles move across each other, what type of interference occurs?

Both A and B (constructive and destructive interference)

How are gravitational and electric force alike?

Both gravitational force and electric force are field forces. Both forces obey the inverse square law.

You have seven resistors available, and all of the resistors have a value of 100.0 ohms. How would you connect these seven resistors to produce an equivalent resistance of 70.0 ohms?

Connect five of the resistors in parallel to produce a 20.0 ohm equivalent resistance. Connect the remaining two resistors in parallel to produce a 50.0 ohm equivalent resistance. Then connect the two groups in series, giving an equivalent resistance of 70.0 ohm.

You have only six resistors available, and all of the resistors have a value of 10.0 ohms. How would you connect these six resistors to produce an equivalent resistance of 12.0 ohms? (Hint: You must use all six resistors.)

Connect five resistors in parallel to produce a 2.0 ohm resistance and then connect the group in series with the remaining 10.0 ohm resistor. This produces an equivalent resistance of 12.0 ohm.

States that the force between two charges varies directly with the product of their charge and inversely with the square of the distance between them.

Coulomb's law

How does the term wave-particle duality of light relate to electromagnetic waves? What are these light particles called? How does the behavior of a high-energy particle compare to a low-energy particle?

Electromagnetic waves exhibit both wave and particle behavior depending on the wave's frequency (or wavelength). When an electromagnetic wave behaves more like a stream of particles, the particles are called photons. A photon is a particle that carries energy but has zero rest mass. A high-energy photon behaves more like a particle, while a low-energy photon behaves more like a wave.

If the force of two current carrying wires is in the same direction, the wires will repel each other.

False

In a magnet, the magnetic field moves negative charges from the north pole to the south pole.

False

Laser light is high powered, directional, coherent, and has a double wavelength.

False

Explain how the right-hand rule describes the magnetic field produced by the current in a straight conductor.

If a wire is grasped in the right hand with the thumb pointing in the direction of the current, the fingers will curl in the direction of the magnetic field. The curling fingers illustrate that the magnetic field induced by a current around a straight conductor forms concentric circles.

Interference in sound is recognized by differences in volume; how is interference in light recognized?

Interference in light is recognized by differences in brightness.

A 9-V battery is in a circuit with three resistors connected in a series. If the resistance of one of the resistors increases, how will the equivalent resistance change?

It will increase.

One of these is equal to 1000 watts that are continously on for 3600 seconds

Kilowatt -hour

Which of the following is true about lasers?

Lasers have many helpful uses in medicine.

Identify one type of electromagnetic wave with a long wavelength. Describe at least two of its applications, and explain why the selected wave's long wavelength is important for both applications.

Radio waves work well for transmitting information across long distances because the long wavelengths can easily travel around objects. Radio waves help scientists understand deep space objects because the long wavelengths of radio waves pass through Earth's atmosphere.

With regard to the flow of electric current, what is resistance?

Resistance is the opposition to electric current by a material or device.

A microwave can reheat 1 cup of coffee in 30 seconds. It takes a coffee-maker 10 minutes to brew 12 cups of coffee. If the coffee-maker requires 900 watts of power and the microwave requires 1200 watts of power, does it require more energy to brew 12 cups with the coffee-maker or reheat 12 cups of coffee in a microwave?

The coffee-maker requires more energy.

What property of the cornea and lens of an eye allows laser light to be transmitted through them?

The cornea and lens are transparent.

What is meant by the statement that a laser produces a narrow beam of coherent light?

The waves emitted by a laser do not shift relative to each other as time progresses. The individual waves behave like a single wave because they are coherent and in phase.

Why is the magnetic field inside a solenoid stronger than the magnetic field outside?

The fields produced by the top and bottom of every loop all point in the same direction and are confined to a small region of space.

What occurs when two electrons are placed above the original proton path and two protons are placed below?

The fired proton curves upward between the two electrons

What happens when a proton is placed directly in the path of the proton cannon?

The fired proton is pushed back toward the gun.

How does the electric force between two charged objects change when the distance between the two objects is doubled? Explain.

The force decreases to one-fourth its previous value because the force is inversely proportional to the square of the distance between the two objects.

How does the electric force between two charged objects change when the charge on one of the objects is doubled? Explain.

The force increases to twice its previous value because the force is directly proportional to the charge on each of the objects.

How is the force on a current carrying conductor calculated?

The force on a current carrying conductor is calculated using the following equation: F = BIl, where F is the magnetic force, B is the magnetic field magnitude, I is the current, and l is the length of the conductor.

Which of the following statements about Earth's magnetic field is true?

The geographic South Pole of Earth and Earth's magnetic north pole are relatively close to each other.

You have a spool of wire, a glass rod, an iron rod, and an aluminum rod. Which rod should you use to make an electromagnet to pick up steel objects? Explain.

The iron rod should be used. Iron will be attracted to a permanent magnet and take on properties of a magnet, whereas aluminum or glass would not.

A negatively charged rubber rod is brought near a neutral, conductive sphere that has no charge. As a result, the part of the sphere closest to the rod becomes positively charged. Explain how this positive charge occurs.

The negatively charged rod repels electrons from the part of the sphere nearest the rod. As a result, this part becomes deficient in electrons, thus acquiring a positive charge.

A positive and negative charge are placed side by side, as shown in the diagram. The positive charge is twice the magnitude of the negative charge. How does this affect the number of electrical field lines that terminate on the negative charge?

The number of field lines that terminate on the negative charge is decreased by one half.

Explain how the polarity of an induced emf in a wire is related to the right-hand rule.

The right-hand rule shows the relationship between the magnetic field, magnetic force, and the velocity of charged particle(s). The polarity of the induced emf depends on the direction in which the wire is moved through the magnetic field. As the right-hand rule indicates, reversing the wire's velocity (motion or direction) will reverse the direction of the magnetic force and thus the polarity of the induced emf.

Two oppositely charged metal spheres are suspended from insulating threads. A negatively charged rod is brought near these spheres. One sphere moves away from the rod, while the other moves toward it. What is the charge of the sphere that moved away from the rod? What is the charge of the sphere that moved toward the rod?

The sphere that moved away from the rod has a negative charge because like charges repel each other. The sphere that moved toward the rod has a positive charge, because unlike charges attract each other.

A particular electrical device operates for the same amount of time each day. If the power line voltage supplied to the device changes by several volts and remains at the new voltage, how will this affect the total daily power consumption of the device?

The total power consumption each day will increase if the voltage increases and will decrease if the voltage decreases.

In the circuit shown above, which resistors, if any, have equal voltages across them?

The voltage Ra is equal to the voltage across Rd and the voltage across Tc is equal to the voltage across Rf.

A change in the number of magnetic field lines through a circular loop will increase or decrease the emf that is produced by the induced current.

True

A magnetic domain is a group of atoms whose magnetic fields are aligned in a common direction.

True

A spectrometer uses a diffraction grating to separate light from a source into its monochromatic components.

True

According to Faraday's law of magnetic induction, as Δt increases, the induced emf decreases, but as Δt decreases, the induced emf increases.

True

An increase in the wavelength of light reaching an optical instrument with a set aperture will cause the resolving power of the instrument to decrease.

True

Faraday's Law of Induction is used to determine the magnitude of the induced emf in a circuit.

True

The cables used to transfer electric energy from the generating station to the consumers must be of low resistance to reduce losses due to joule heating.

True

The electric field around a proton can be represented by lines of force that point outward from the proton.

True

The equation d sin ... is used to calculate the fringe positions for a diffraction grating.

True

The space around a charged object contains an electric field.

True

How is a stable interference pattern produced?

Two sources are needed. Each source must produce a traveling periodic wave and the phases of the individual waves with respect to each other must be constant.

Identify one type of electromagnetic wave with a short wavelength. Describe at least two of its applications, and explain why the selected wave's short wavelength is important for both applications.

Ultraviolet light is used as a disinfectant to kill bacteria because the UV wave's short wavelength (and high frequency) have enough energy to destroy these organisms. UV light is also used to study the chemical makeup of atoms and molecules because the short wavelengths increase resolution and permit scientists to study atomic structures.

A blow dryer draws 11 A when it is connected to 125 V. If electrical energy costs $0.090/kW·h, what is the cost of using the blow dryer for exactly 15 min?

d. $0.031

A microwave draws 5.0 A when it is connected to a 120 V outlet. If electrical energy costs $0.090 per kW·h, what is the cost of running the microwave for exactly 6 h?

d. $0.32

Two point charges, initially 1 cm apart, are moved to a distance of 3 cm apart. By what factor do the resulting electric and gravitational forces between them change?

d. 1/9

An electric toaster requires 1100 W at 110 V. What is the resistance of the heating coil?

d. 11 ohms

A 0.50 muF capacitor is connected to a 12 V battery. Use the expression PE = 1/2C(DV)^2 to determine how much electrical potential energy is stored in the capacitor.

d. 3.6 × 10^-5 J

A positive test charge of 6.00 µC is placed in an electric field, which exerts a force of 5.00 x 10^-4 N on the test charge. What is the magnitude of the electric field strength at the location of the test charge?

d. 83.3 N/C

Tripling the current in a circuit with constant resistance has the effect of changing the power by what factor?

d. 9

Find the magnitude of the electric field strength at a position that is 0.6 m from a point charge of 3.6 x 10-6 C.

d. 9.0 x 10^4 N/C

How is a motor's mechanical energy able to perform mechanical work?

d. A shaft connected to the rotating coil is attached to some external device.

Which is the most correct statement regarding the drawing of electric field lines?

d. Electric field lines never cross each other.

Which of the following is not true for both gravitational and electric forces?

d. Forces are either attractive or repulsive.

What effect will be produced on a capacitor if the separation between the plates is increased?

d. It will decrease the capacitance.

What occurs when two charges are moved closer together?

d. The force between the charges increases.

A stationary positive charge, Q, is located in a magnetic field, B, which is directed toward the right. What is the direction of the magnetic force on Q?

d. There is no magnetic force

Which of the following statements about X rays is incorrect?

d. X rays can easily penetrate bones and any thick material.

Which of the following modifications to a solenoid would be most likely to decrease the strength of its magnetic field?

decreasing the current and reducing the number of coils

The dark regions are areas of __________ interference.

destructive

A superposition of two or more waves in which individual displacements on opposite sides of the equilibrium position are added together to form the resultant wave.

destructive interference

Produces dark fringes

destructive interference

The dark lines in a double-slit interference pattern are due to _______.

destructive interference

The lines of the magnetic field around a current-carrying wire

form concentric circles around the wire

A change in the direction of a wave when the wave encounters an obstacle, an opening, or an edge.

diffraction

The table below shows a list of some electric appliances with the values of their potential differences and current. Which appliance consumes the most power?

drill

A flow of charged particles.

electric current

The field that exists around any charged object; produces forces that can do work, transferring energy from the field to another charged object.

electric field

Lines that provide a picture of an electric field, indicate the field's strength by the spacing between the lines, never cross, and are directed toward negative charges and away from positive charges.

electric field line

Used to represent the electric field in space around a charge

electric field lines

The magnitude of an electric field at a point in the field, equal to the force that would be exerted on a small unit charge placed at the point.

electric field strength

In a non-uniform electric field, this is equal to work/charge

electric potential difference

The change in potential energy per unit charge in an electric field.

electric potential difference

A __________ wave is a wave that consists of changing electric and magnetic fields.

electromagnetic

The process of creating a current in a circuit by a changing magnetic field.

electromagnetic induction

What is the process of causing a current in a circuit using a changing magnetic field called?

electromagnetic induction

The transfer of energy associated with an electric and magnetic field; it varies periodically and travels at the speed of light.

electromagnetic radiation

An object that has a negative electric charge has an abundance of atomic particles called ____________________.

electrons

When a glass rod is rubbed with silk and becomes positively charged,

electrons are removed from the rod.

A device that is used to detect electric charges and consists of a metal knob connected by a metal stem to two thin metal leaves.

electroscope

The study of electric charges that can be collected and held in one place.

electrostatics

The magnitude of the charge of an electron.

elementary charge

The electric potential difference of zero between two or more positions in an electric field.

equipotential

For resistors in a series, is the sum of all the individual resistances.

equivalent resistance

When a conducting sphere is charged positively, initially the charge is deposited on the left side. However, due to the sphere's conducting nature, the charge spreads uniformly throughout the surface of the sphere. Charge is uniformly distributed because:

excess electrons within the sphere move toward excess protons.

A current in a long, straight wire produces a magnetic field. These magnetic field lines

form circles that go around the wire

Electricity may be generated by moving a magnet through the center of a loop of wire. The induced emf is greatest when the plane of the loop __________ the magnetic field.

is perpendicular to

An energy unit used by electric companies to measure energy sales: 1 kWh is equal to 1000 watts, W, delivered continuously for 3600 s (1 h).

kilowatt-hour

A device that produces coherent light of only one wavelength.

laser

Which of the following is a device that produces an intense, nearly parallel beam of coherent light?

laser

A repelling force occurs between two charged objects when the charges are of

like signs.

In a magnetized substance, the domains

line up mainly in one direction.

The number assigned to interference fringes relative to the central bright fringe.

order number

A region composed of a group of atoms whose magnetic fields are aligned in the same direction.

magnetic domain

A region where a magnetic force can be detected.

magnetic field

________ waves require a medium to travel, while _______ waves do not require a medium to travel.

mechanical; electromagnetic

Induces an emf in a coil that will reduce the current in order to create mechanical energy

motor

The ability of one circuit to induce an emf in a nearby circuit in the presence of a changing current.

mutual inductance

A bar magnet falls through a loop of wire with constant velocity, and the north pole enters the loop first. The induced current will be greatest when the magnet is located so that the loop is

near either the north or the south pole.

An atom whose positively charged nucleus exactly balances the negative charge of the surrounding electrons.

neutral

According to Lenz's law, the magnetic field of an induced current in a conductor will

oppose a change in the applied magnetic field.

A property that determines how much current will flow; is equal to voltage divided by current.

resistance

A device with a specific resistance; may be made of long, thin wires, graphite, or semiconductors and often is used to control the current in circuits or parts of circuits.

resistor

The ability of an optical instrument to form separate images of two objects that are close together.

resolving power

What term describes the ability of an instrument to separate two images that are close together?

resolving power

A method used to determine the direction of a magnetic field relative to the direction of conventional current.

right hand rule

Root-mean-square; the square root of the arithmetic mean of the squares of the numbers in a given set of numbers.

rms

The value of alternating current that gives the same heating effect that the corresponding value of direct current does.

rms current

In most electric generators, either the armature or the magnetic field is ____, generating a(n) ____.

rotated; induced current

A type of electric circuit in which all current travels through each device and is the same everywhere; its current is equal to the potential difference divided by the equivalent resistance.

series circuit

A type of connection in which there is only a single current path.

series connection

Occurs when a very low resistance circuit is formed, causing a very large current that could easily start a fire from overheated wires.

short circuit

The equivalent resistance of a complex circuit is usually determined by

simplifying the circuit into groups of series and parallel circuits.

The __________ makes contact with the coil of an AC generator.

slip rings

A long coil of wire with many loops; fields from each loop add to the fields of the other loops, creating a greater total field strength.

solenoid

Produces a vertical magnetic field that circles the coils

solenoid

If the secondary emf is less than the primary emf, what kind of transformer is used?

step-down transformer

What kind of transformer has more turns in the primary coil than in the secondary coil?

step-down transformer

A material with zero resistance that can conduct electricity without a loss of energy.

superconductor

A device built to observe distant objects by making them appear closer.

telescope

Which statement describes Earth's magnetic declination?

the angle between true north and north indicated by a compass

One farad is equal to one coulomb per

volt

The unit equal to one joule per coulomb, 1 J/C.

volt

The unit of electric potential difference is the

volt.

A measure of the difference in electric potential between two points in space, a material, or an electric circuit, expressed in volts.

voltage

A series circuit that is used to produce a voltage source of desired magnitude from a higher-voltage battery; often is used with sensors such as photoresistors.

voltage divider

A high-resistance device used to measure the voltage drop across any portion or a combination of portions of a circuit and is connected in parallel with the part of the circuit being measured.

voltmeter

What are the three quantities that can express the electromagnetic spectrum?

wavelength, frequency, and energy

Is it possible to find the voltage of the second lamp in a parallel circuit if one lamp has a voltage of 12 V?

yes

Ideally, the resistance of an ammeter should be:

zero

Two loops of wire are arranged so that a changing current in the primary will induce a current in the secondary. The secondary loop has twice as many turns as the primary loop. As long as the current in the primary is steady at 3.0 A, the current in the secondary will be

zero