cp2 unit 3

Magnetic domains are usually randomly oriented. This can be changed by

Bringing a magnet close to the sample

How many time constants does it take to discharge a capacitor in an RC circuit?

Never fully discharged but 5 is accepted as the time it takes

Which element listed below is ferromagnetic?

Nickel, iron, cobalt

What rule is used to determine the force on a current carrying wire due to a magnetic field?

RHR

The electromagnetic spectrum consists of

Radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays

Two parallel loops of wire with current moving in the same direction are near each other with an imaginary line connecting the centers of both loops and passing through the loops. What is the force between them?

attractive

what is the eq. resistance when R1,R2,R3 are connected in parallel

(1/R1+ 1/R2+ 1/R3)^-1

Which laser pointer (red or violet) outputs the higher energy photons?

violet

The parts of the electromagnetic spectrum that can ionize molecules and/or atoms are

Ultraviolet, x-rays and gamma rays

To measure the potential difference at a circuit element a voltmeter must be connected

In parallel with the element to be tested

To measure current in a circuit the ammeter must be connected

In series with the circuit elements

The Earth's magnetic north pole is

Near Earth's south geographic pole

In a circuit model of nerve-impulse propagation, what would happen to the propagation speed if the myalin sheath thickness were larger?

Speed would increase

Changing the angle of a wire loop relative to a magnetic field changes

The magnetic flux

Faraday's law of electromagnetic induction helps determine

The magnitude of induced emfs and currents

how are car headlights connected

parallel

When the north pole of the magnet moves toward the copper a magnetic field is induced in the copper. What direction is the force between the copper and the magnet?

repulsive

The polarization of electromagnetic waves refers to the orientation of

the electric field

A cell phone emits EM waves at 1.9 GHz and a microwave oven emits EM waves at 2.4 GHz. Which one emits the shorter wavelength?

the microwave

How do you determine the magnetic force on a negatively charged object moving through a magnetic field?

use the RHR then reverse the direction of force

Magnetic field lines point from

From north magnetic poles to south magnetic poles

What is the current in a circuit with a 10 V battery and 1000 ohms of resistance?

10 mA

A circuit consists of 1 battery and 2 identical resistors connected in parallel to the battery. The battery has an emf of 12 V. What is the potential difference across the first resistor?

12 V

A circuit consists of 1 battery and 2 identical resistors connected in series with the battery. The battery has an emf of 12 V. What is the potential difference across both resistors?

12V

the eq. resistance of 2 identical resistors with resistance R which are connected in series is

2R

15. An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?A) The spring will contract, raising the weight.B) The spring will extend, lowering the weight.C) The weight will not move.D) The spring will begin to swing like a pendulum.E) None of these are true.

A

23. An electromagnetic wave is propagating towards the west in free space. At a certain moment the direction of the magnetic field vector associated with this wave points vertically upward. What is the direction of the electric field vector? A) horizontal and pointing south B) vertical and pointing down C) horizontal and pointing north D) vertical and pointing upward E) horizontal and pointing east

A

24. Increasing the brightness of a beam of light without changing its color will increase A) the number of photons per second traveling in the beam. B) the energy of each photon. C) the speed of the photons. D) the frequency of the light. E) the wavelength of the photons.

A

4. Four unequal resistors are connected in a parallel with each other. Which one of the following statements is correct about this combination?A) The equivalent resistance is less than that of the smallest resistor.B) The equivalent resistance is equal to the average of the four resistances.C) The equivalent resistance is midway between the largest and smallest resistance.D) The equivalent resistance is more than the largest resistance.E) None of the other choices is correct.

A

8. A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about this circuit? A) The charge on the capacitor after four time constants is about 98% of the maximum value. B) The charge on the capacitor after one time constant is 50% of its maximum value. C) The charge on the capacitor after one time constant is 1/e of its maximum value. D) The voltage on the capacitor after one time constant is 1/e of the maximum value. E) The voltage on this capacitor after one time constant is 100% of its maximum value.

A

9. An uncharged capacitor is connected in series with a resistor, a dc battery, and an open switch. At time t =0 s, the switch is closed. Which of the graphs below best describes the charge Q on the capacitor as a function of time t?

A charge increases with time quadratically

When two or more different capacitors are connected in series across a potential source, which of the following statements must be true? (There could be more than one correct choice.) A) The total voltage across the combination is the algebraic sum of the voltages across the individual capacitors. B) Each capacitor carries the same amount of charge. C) The equivalent capacitance of the combination is less than the capacitance of any of the capacitors. D) The potential difference across each capacitor is the same. E) The capacitor with the largest capacitance has the most charge.

A B C

When two or more different capacitors are connected in parallel across a potential source (battery), which of the following statements must be true? (There could be more than one correct choice.) A) The potential difference across each capacitor is the same. B) Each capacitor carries the same amount of charge. C) The equivalent capacitance of the combination is less than the capacitance of any one of the capacitors. D) The capacitor with the largest capacitance has the largest potential difference across it. E) The capacitor with the largest capacitance has the most charge.

A E

Induced current is current created by

A changing magnetic field

Two current carrying wires parallel to each other exert

A repulsive or attractive force depending on the directions of the currents

Several capacitors are connected in series with a battery. The potential difference across each capacitor

Adds to equal the emf of the battery

How are radio waves created?

An oscillating dipole causes an oscillating electric field which induces an oscillating magnetic field

12. When the switch is closed in the circuit shown in the figure, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet isA) a north magnetic pole.B) a south magnetic pole.C) There is not enough information given to answer the question.

B

Current in a wire creates a magnetic field

Around the wire

14. Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the magnetic force that each wire exerts on the other? A) It is doubled. B) It stays the same. C) It is tripled. D) It is quadrupled. E) It is reduced by a factor of two.

B

18. A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases? A) counterclockwise B) clockwise C) clockwise initially, then counterclockwise before stopping D) There is no induced current in this coil.

B

19. An outer metal ring surrounds an inner metal ring, as shown in the figure. The current in the outer ring is counterclockwise and decreasing. What is the direction of the induced current in the inner ring? A) clockwise B) counterclockwise C) There is no induced current in the inner ring.

B

20. A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is pulled upward, what is the direction of the current induced in the ring, as viewed from above? A) There is no current in the ring. B) counterclockwise C) clockwise

B

What magnetic field, B, is needed to create a motional emf for a conductor moving at speed v that is d long.

B = emf/(vd)

How does the magnetic field, B, of a current carrying wire depend on the current, I, and the distance, r, from the wire?

B is proportional to I/r

The force needed to pull a wire along conducting rails in a magnetic field is proportional to

B^2

10. Which one of the following statements is correct?A) Earth's geographic north pole is the north pole of Earth's magnetic field.B) Earth's geographic south pole is the south pole of Earth's magnetic field.C) The north pole of a magnet points towards Earth's geographic north pole.D) The north pole of a magnet points towards Earth's geographic south pole.E) None of the above statements is correct.

C

11. A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle A) causes the particle to speed up. B) causes the particle to slow down.C) causes the particle to accelerate. D) is in the same direction as the particle's velocity.E) is opposite the direction of the particle's velocity.

C

13. When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of the new magnetic force on each wire?A) 16F B) 8F C) 4F D) 2F E) F

C

17. A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is A) parallel to the magnetic field. B) at 45° with the magnetic field. C) perpendicular to the magnetic field.

C

22. In an electromagnetic wave in free space, the electric and magnetic fields are A) parallel to one another and perpendicular to the direction of wave propagation. B) parallel to one another and parallel to the direction of wave propagation. C) perpendicular to one another and perpendicular to the direction of wave propagation.D) perpendicular to one another and parallel to the direction of wave propagation.

C

7. Kirchhoff's loop rule is a statement ofA) the law of conservation of momentum.B) the law of conservation of charge.C) the law of conservation of energy.D) the law of conservation of angular momentum.E) Newton's second law.

C

What is the equivalent capacitance for capacitors C1, C2, and C3 when they are connected in parallel?

C1+C2+C3

Cell walls can be modeled as what electric element(s)?

Capacitors and resistors

The auroras near Earth's north and south poles are created by

Charged particle from the sun interacting with Earth's magnetic field

16. Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. If the magnetic field strength at the center of the smaller loop is B, what is the magnetic field strength at the center of the larger loop? A) 8B B) 4B C) 2B D) B/2 E) B/4

D

21. Which one of the following lists gives the correct order of the electromagnetic waves from longer wavelength to shorter wavelength? A) radio waves, infrared, microwaves, ultraviolet, visible, x-rays, gamma rays B) radio waves, ultraviolet, x-rays, microwaves, infrared, visible, gamma rays C) radio waves, microwaves, visible, x-rays, infrared, ultraviolet, gamma rays D) radio waves, microwaves, infrared, visible, ultraviolet, x rays, gamma rays E) radio waves, infrared, x-rays, microwaves, ultraviolet, visible, gamma rays

D

5. You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct?A) Both bulbs glow with the same brightness, but less than their normal brightness.B) Both bulbs glow with the same brightness, but more than their normal brightness.C) The 100-W bulb glows brighter than the 50-W bulb.D) The 50-W bulb glows more brightly than the 100-W bulb.

D

6. You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct?A) Both bulbs glow with the same brightness, but less than their normal brightness. B) Both bulbs glow with the same brightness, but more than their normal brightness. C) The 100-W bulb glows brighter than the 50-W bulb.D) The 50-W bulb glows more brightly than the 100-W bulb.

D

The exponential behavior of an RC circuit occurs

During charging and discharging of the capacitor

Four unequal resistors are connected in series with each other. Which one of the following statements is correct about this combination?A) The equivalent resistance is equal to that of any one of the resistors.B) The equivalent resistance is equal to average of the four resistances.C) The equivalent resistance is less than that of the smallest resistor.D) The equivalent resistance is less than that of the largest resistor. E) The equivalent resistance is more than the largest resistance.

E

Which of these equations is correct for the energy of a photon?

E = hf

What is the magnetic force, F, on a wire of length L carrying current I, in a magnetic field B?

F=ILB

What is the property of the copper in the track that leads to the braking force on the toy car?

Good electrical conductor

Refrigerator magnets

Have multiple poles arranged as long U-magnets

The induced current, I, due to an induced emf is

I = emf/R

RC circuits can be used for

Intermittent wipers on your car Flashing lights on bicycles Timing in computers

The magnetic field inside a current loop

Is in the opposite direction as the field outside the loop

The magnetic field of a solenoid

Is stronger inside the solenoid than outside

What law describes the directions of eddy currents produced when a conductor moves through a magnetic field?

Lenz

Magnets attract

Magnetic materials

MRI's use what property of atoms to produce images?

Magnetic moment of the nucleus

The potential difference created by moving a conductor in a magnetic field is called

Motional emf

Which of these is a way to create a changing magnetic field?

Moving a circuit relative to a magnet Opening or closing a switch in a circuit Moving a magnet relative to a circuit

The induced current due to a changing magnetic flux produces a magnetic field which

Opposes the change of the flux

The force on a moving charged object in a magnetic field is

Perpendicular to both the magnetic field and the object's velocity

The equivalent resistance of 2 identical resistors, with resistance R, which are connected in parallel is

R/2

what is the eq. resistance when R1 R2 and R3 are connected in series

R1+R2+R3

The time constant for an RC circuit is

RC

When current flows in a counterclockwise direction in a current loop the magnetic field created points to the left. What is the field direction when the current is reversed?

Right

What rule is used to determine the direction of the magnetic field created by a current moving in a wire?

Right hand rule

In order for an electric motor to work

The current must change direction every half cycle

A current loop has a magnetic dipole moment equal to

The current times the area of the loop

Magnetic flux refers to how much magnetic field goes through a loop. The flux depends on the magnetic field and

The effective area of the loop

A photon is

The particle aspect of an electromagnetic wave

The equivalent capacitance of 2 capacitors connected in parallel is

The sum of the capacitances

When capacitors are connected in series

They have the same charge

Cutting a permanent magnet in half creates

Two weaker magnets

Which part of the electromagnetic spectrum listed below is the most particle like?

X rays

The electric field and magnetic field of an electromagnetic wave

are perpendicular are in phase are related to the speed of light

An electromagnetic flowmeter can be used to measure the velocity of

blood and water

Which animal has 4 types of cones in their eyes?

chicken

A changing electric field

creates an induced magnetic field

kirchoffs junction law states that

current into a junction = current leaving it

The speed of an electromagnetic wave

is equal to the speed of light

Several capacitors are connected in series with a battery. The charge on the capacitors

is the same for each capacitor

The path of a charged object in a magnetic field depends on

mass, velocity, charge

kirchoffs loop law says

potential difference around a loop =0

what circuit element has a zig zag for its symbol

resistor

Computer hard disks

store data using magnetic fields

in a series circuit with 2 resistors

the current flows through one resistor then the next

in a parallel circuit with 2 resistors

the current splits and flows through both resistors at the same time

The circuit is constructed so that the blue LED comes on if the current is in one direction and the orange LED comes on if the current is in the other direction. The blue LED comes on when the magnet is quickly placed on the coil. As the magnet is quickly removed from the coil what will happen?

the orange LED comes on

The magnetic field of a solenoid does not depend on

the radius of the solenoid

What direction is the magnetic force on a proton moving in the same direction as a magnetic field?

there is no force