Physics Exam #4
A heater draws 20A when connected to a 110-V line. If the electric power costs 20 cents per kilowatt hour, the cost of running the heater for 10 hours is
$4.40
Electrons can be transferred from one place to another by the process of
-Electrons can be transferred from one place to another by the process of contact, which means touching. -induction, which means non-touching. -friction.
The operation of a microwave oven makes use of
-an oscillating electric field. -flip flopping of polarized molecules. -the polar nature of water molecules.
Electric shielding within a conductor is a consequence of
-cancellation of electric field lines. -the balancing of opposing forces. -both the attraction and repelling nature of electricity.
By convention, the direction of current in a circuit is
-from the positive terminal of a source to the negative terminal. -the direction in which positive charge flows.
A suitable electric pump in an electric circuit is a
-generator -chemical battery
Every isolated proton in the universe is surrounded by its own
-gravitational field. -electric field.
Ohm's law tells us that the amount of current produced in a circuit is
-inversely proportional to resistance. -directly proportional to voltage.
In a circuit powered by a battery, charge
-is energized by the battery. -flows through the battery.
A balloon will stick to a wooden wall if the balloon is charged
-negatively -positively
When a pair of identical lamps are connected in parallel
-power dissipated in each is the same. -current in each is the same. -voltage across each is the same.
Current in a conductor can be increased by
-reducing its resistance. -increasing the voltage across it.
Two charged particles held close to each other are released. As they move, their speeds increase. Therefore, their charges have
-same signs -opposite signs
An aurora borealis high above the atmosphere is due to
-trapping of charged particles by Earth's magnetic field. -fountains of high-speed charged particles. -disturbances in Earth's magnetic field.
Between a pair of equal and opposite charges, field lines are
-vectors, with patterns that stem from the inverse-square law. -more concentrated closer to the charges. -directed from positive to negative.
Electric charge distributes itself on conducting surfaces
-with greater concentration on more curved parts. -such that the electric field inside is zero.
CHAPTER 22
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CHAPTER 23
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CHAPTER 24
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Two charges separated by one meter exert 1-N forces on each other. If the charges are pulled 3 meters apart, the force on each charge will be
0.11 N
The amount of current in a CFL rated 23W 120V is about
0.2 A
A 60-W light bulb connected to a 120-V source draws a current of
0.5 A
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about
0.55 ohm
The amount of current in an incandescent bulb rated 75W 120V is about
0.6 A
An electron is pushed into an electric field where it acquires a 1-V electrical potential. If two electrons are pushed the same distance into the same electric field, the electrical potential of the two electrons is
1 V
When a pair of 1-ohm resistors are connected in series, their equivalent (combined) resistance is 2 ohms, and when connected in parallel is
1/2 ohm
Assume that 10 J of work pushes a charge initially at rest into an electric field. If the charge is then released, it flies back to its starting position with a kinetic energy of
10 J
If 10 J of work is used in pushing 1 C of charge into an electric field, its electric potential relative to its starting position is
10 V
A 60-W and a 100-W light bulb are connected in parallel to a 120-V outlet. Which bulb draws more current?
100 w bulb
The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is
12 ohms
A power line with a resistance of 2 ohms carries a current of 80 A. The power dissipated in the line is
12,800 w
Two charges that are separated by one meter exert 1-N forces on each other. If the charges are pushed together so the separation is 25 centimeters, the force on each charge will be
16 N
A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of
2.4 ohms
The current in two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is
220 ohms
When a 12-V battery powers a single 6-ohm lamp
24 joules flow in the lamp each second.
The electric power supplied to a lamp that carries 2 A at 120 V is
240 Watts
Which of the battery arrangements will light the lamp?
3
The electrical force on a 2-C charge is 60 N. The electric field where the charge is located is
30 N/C
The power dissipated in a 4-ohm resistor carrying 3 A is
36 W
Two charges that are separated by one meter exert 1-N forces on each other. If the magnitude of each charge is doubled, the force on each charge is
4 N
An electric heater is rated 300W 110V. The safety fuse in the circuit can withstand 15 A of current. How many heaters can be safely operated in the circuit?
5
The resistance of a filament that carries 2 A when a 10-V potential difference across it is
5 ohms
Three resistors take the shape of a triangle, one resistor in each leg. Resistance in one leg is 4 ohms, 6 ohms in a second leg, and a third leg 10 ohms. Connecting an ohm-meter across the 10-ohm resistor will show the equivalent resistance to be
5 ohms
A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with
6 joules
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about
6 ohms
Three 10-ohm resistors take the shape of a triangle, one resistor in each leg. Connecting an ohm-meter across any two points of the triangle will show the equivalent resistance to be
6.7 ohms
A 60-W and a 100-W light bulb are rated at 120V. Which bulb has a higher resistance?
60 W bulb
The power consumed by a device drawing 0.8 A when connected to 120 V is
96 W
Two charged particles attract each other with a force F. If the charges of both particles are doubled, and the distance between them also doubled, then the force of attraction will be
F
Two charged particles repel each other with a force F. If the charge of both particles is tripled and the distance between them is also tripled, then the force will be
F
Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be
F/2
Imagine a single charge q placed at one corner of a square, and that the electric field at the center of the square is F/q. If two other equal charges are placed at the adjacent corners of the square (leaving the opposite corner "blank"), the electric field at the center of the square is
F/q.
Given that k=9.0×109N⋅m2/C2 (the proportionality constant for Coulomb's law), select the correct equations that show that the force between the charges is 5.76×1011N
F=kq1q2r2=(9.0×109N⋅m2/C2)⋅(0.8C)⋅(0.8C)(0.1m)2=5.76×1011N
Given that k=9.0×109N⋅m2/C2 (the proportionality constant for Coulomb's law), select the correct equations that show that the force between the charges is 6.4×1010N.
F=kq1q2r2=(9.0×109N⋅m2/C2)⋅(0.8C)⋅(0.8C)(0.3m)2=6.4×1010N
An electron volt, eV, is a unit of energy. Which is larger, a GeV or a MeV?
GeV
A proton moves in a circular path perpendicular to a constant magnetic field. If the field strength of the magnet is increased, does the diameter of the circular path increase, decrease, or remain the same?
The diameter of the circular path decreases.
A galvanometer indicates
a flow of electrons
Although electrons in metal move in haphazard directions at many times the speed of sound, the drift speed of electrons that compose electric current is
a fraction of a centimeter per second.
Electrons flow in a wire when there is
a potential difference across its ends.
The direction of an electric field is the direction of the force exerted on
a proton
A common naturally-polarized bit of matter is
a water molecule
Superconductors are noted for their
absence of electric resistance.
The electric field established by a battery in a dc circuit
acts in one direction
The magnetic fields of a pair of nearby magnets can
add or subtract by vector rules.
Magnetic fields are produced by
all moving electrical charges.
It is correct to say that in electric circuits
all of the above
When current reverses direction in a wire, the surrounding magnetic field
also reverses direction
Current that is typically 60 hertz is
alternating current
The equivalent resistance of any parallel branch in a circuit is
always less than the resistance of the lowest resistor.
In units of measurement, power in watts is equal to
amperes x volts
A current-carrying coil of wire is
an electromagnet
If you wish to keep chicken warm in a shed on a cold night, the best lamp to use is
an incandescent lamp
A semiconductor can be
an insulator or conductor
Surrounding every magnet is
an magnetic field
In general, a common magnet has
at least two poles
The direction of the force exerted on a moving charge in a magnetic field is
at right angles to the direction of the motion.
The source of electrons that illuminate a common lamp in your home is
atoms in the lamp filament.
Like kinds of magnetic poles repel while unlike kinds of magnetic poles
attract
The pair of protons in the nucleus of a helium atom
attract a pair of orbiting electrons.
An electron and a proton
attract each other
Biomagnetism has been detected in
bacteria. pigeons. wasps. humans.
Direct current is normally produced by a
battery
A reason for electric shielding inside a conductor is that any free electrons inside would
be set in motion until equilibrium is established, on the outside.
When a current-carrying wire is bent into a loop, its magnetic field inside the loop
becomes concentrated
An uncharged pith ball is suspended by a nylon fiber. When a negatively-charged rubber rod is brought near the pith ball, without touching, the ball
becomes polarized
Electrostatics is a branch of electricity that focuses on
both of these when static
A 60-W and a 100-W light bulb are connected in series to a 120-V outlet. Which bulb draws more current?
both the same
It is said that electric charge is conserved, which means that electric charge
can be neither created nor destroyed.
In the atoms of most materials the fields of individual electrons
cancel one another
Whereas electric charges can be isolated, magnetic poles
cannot
The electric field established by a generator in an ac circuit
changes magnitude and direction with time.
An electric diode is useful for
changing ac to dc
Electric potential, measured in volts, is the ratio of electric energy to the amount of electric
charge
Normally a small party balloon charged to several thousand volts will have a relatively small amount of
charge and energy
Which statement is correct?
charge flows in a current
If you rub an inflated balloon against your hair and place the balloon against the wall it will stick to the wall, illustrating
charge polarization
Magnetic compasses reportedly were first used for navigation by
chinese sailors
Magnetic field lines about a current-carrying wire
circle the wire in closed loops
The shape of a magnetic field surrounding a current-carrying conductor is
circular
The electrical force between charges is strongest when the charges are
close together
An electroscope is charged positively as indicated by foil leaves that stand apart. As a negative charge is brought close to the electroscope, the leaves become
closer together
Magnetic field strength about a magnet is strongest where magnetic field lines are
closer together
An ampere is a unit of electric
current
Power is defined as the energy expended per unit of time. When translated to electrical terms, power is equal to
current multiplied by voltage
As more lamps are connected in a series circuit, the overall current in the power source
decreases
When an electron passes through the magnetic field of a horseshoe magnet, the electron's
direction is changed
The primary purpose of a lightning rod is to
discharge the structure to which it is attached.
To weaken a bar magnet
drop it on a hard surface. put it in hot flames. whack it with a hammer.
Solar winds headed in Earth's direction are deviated mainly by
earth's magnetic field
When Eddie Electron experiences an electrical shock, the source of electrons composing the shock is
eddie's body
An initially unmagnetized iron nail is placed near one of the poles of a magnet. An iron nail is more strongly attracted to the magnet if the nearest pole of the magnet to the nail is the
either of these
A galvanometer can be calibrated to measure
electric current. electric voltage.
When we say an appliance "uses up electricity," we mean
electric energy dissipates into heat.
Which force field can increase a moving electron's speed?
electric field
Surrounding every moving electron is
electric field magnetic field
Which force field can accelerate an electron?
electric field magnetic field
The current produced by voltage in a circuit is impeded by
electric resistance
The force that binds atoms together to form molecules is
electrical
The fundamental force underlying all chemical reactions is
electrical
Two protons attract each other gravitationally and repel each other electrically. The stronger of these two forces is
electrical
Just as "gravity" is the study of a wide range of gravitational interactions, "electricity" is the study of a wide range of
electrical interactions.
A proton and an electron are placed in an electric field. Which undergoes the greater acceleration?
electron
Electrons that are energized to glow in the filament of a common ac lamp are
electrons already in the filament
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus
For electric current in the home, your power company supplies
energy
One kilowatt-hour is a unit of
energy
Lillian safely touches a 100,000-volt Van de Graaff generator. Although the voltage is high, the relatively small amount of charge means a relatively small amount of
energy transfer
Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is
equally huge
Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is
exactly 100 N
The cause of electrical shock is predominantly
excess voltage
A current-carrying loop of wire experiences no tendency to rotate in a magnetic field when
field lines pass directly through the loop.
A circuit breaker often serves the same purpose as a
fuse
To become a negative ion, an atom must
gain an electron
Alternating current is normally produced by a
generator
A 100-W lamp glows brighter than a 25-W lamp. The current drawn by the 100-W lamp is
greater
A compass is moved from the Northern Hemisphere to the Southern Hemisphere. Assume that the only magnetic field that acts on the compass is the Earth's magnetic field, and that this field is the same as the field of a dipole with the locations of the poles described in the textbook. When the compass is moved through the equator, the magnetic needle of the compass will change direction relative to the meridian
hardly at all
Over geologic history the Earth's magnetic field
has reversed direction many times.
If you break a bar magnet in half you'll
have two magnets.
A beam of singly-charged ions entering a magnetic field with the same speed are swept into circular paths. The wider paths are those of
heavier ions
Just as water flows from a region of high pressure to a region of low pressure, electric charge flows from a region of
high electric pressure to a region of low electric pressure.
To connect a pair of resistors so that their combined (equivalent) resistance will be less than the resistance of either one, should you connect them in series or in parallel?
in parallel
To connect a pair of resistors so that their combined (equivalent) resistance will be greater than the resistance of either one, should you connect them in series or in parallel?
in series
Place an iron rod inside a current-carrying coil of wire and you
increase the strength of the electromagnet.
When you turn on a lamp, the initial current in its filament is greater at first, rather than a moment later, which indicates
increased temperature means increased resistance.
A positive charge and a negative charge held a certain distance apart are released. As they move, the force on each particle
increases
As more lamps are connected in a parallel circuit, the overall current in the power source
increases
Heat a copper wire and its electric resistance
increases
If you stretch a copper wire so that it is thinner, the resistance between its ends
increases
Electrons flow in an electrical circuit by
interacting with an established electric field.
An electrically charged atom is an
ion
Magnetic domains normally occur in
iron
It is said that electric charge is quantized, which means that the charge on an object
is a whole-number multiple of the charge of one electron.
To say that an object becomes electrically polarized means that
its charges have been rearranged.
A 100-W lamp glows brighter than a 25-W lamp. The electrical resistance of the 100-W lamp is
less
Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry
less current
If two copper wires of the same length have different thickness, then the thicker wire has
less resistance
The amount of current in an LED bulb rated 10.5W 120V is
less than 1 A
The drift speed of electrons that compose current in a flashlight is about
less than 1 cm/s
When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is
less than the resistance of either lamp.
Conducting materials are composed of atoms with
loose outer electrons
Charge carriers in a metal are electrons rather than protons because electrons are
loosely bound
To become a positive ion, an atom must
lose an electron
Superconductors most often require
low operating temperatures
Two light bulbs are connected to a battery, one at a time. The bulb that draws more current has the
lower resistance, it is brightest
Wood does not have magnetic properties because it contains no
magnetic domains
Into which stable force field can a proton be placed at rest without being acted upon by a force?
magnetic field
Pigeons navigate primarily by
magnetic sensors in their heads.
The electrical force between electric charges depends only on their
magnitude and separation distance
An electron beam directed through a magnetic field
may be deflected. may experience a force.
A current-carrying wire in a magnetic field
may experience a force. may be deflected.
A compass needle in a magnetic field
may experience a pair of torques.
Electric resistance in our skin is lowered when our skin is
moist
Connect a pair of lamps in series and current is drawn from the battery. Connect the same lamps in parallel and the current drawn is
more
Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry
more current
The voltage across a 10-ohm resistor carrying 5 A is
more than 20 V
When two lamps are connected in series to a battery, the electrical resistance that the battery senses is
more than the resistance of either lamp.
An uncharged pith ball is suspended by a nylon fiber. When a positively-charged rubber rod is brought nearby, the pith ball
moves toward the rod
The source of all magnetism is
moving electric charge
Much of the charge on a conducting cube is
mutually repelled toward its corners.
If you comb your hair and the comb becomes positively charged, then your hair becomes
negatively charged
Rub electrons from your hair with a comb and the comb becomes
negatively charged
A positively-charged rod is held near an aluminum can that rests on a dry wood table. If you momentarily touch the opposite side of the can with your finger, the can becomes
negatively charged.
To say that electric charge is conserved means that no case has ever been found where
net charge has been created or destroyed.
Which of these does NOT have an electrical charge?
neutron
No net force acts on a loop of wire in a magnetic field when
no magnetic field lines pass through the loop. no current is in the loop.
A conductor differs from an insulator in that a conductor has more
none of the above
A lamp rated at 120W 120V has a filament resistance of
none of the above
Imagine a single charge q placed on one corner of a square, and that the electric field at the center of the square is F/q. If additional equal charges are placed on the other three corners, the electric field at the center of the square due to these four equal charges is
none of the above
The electric field around an isolated electron has a certain strength 1 cm from the electron. The electric field strength 2 cm from the electron is
none of the above
The electric field inside the dome of a Van de Graaff generator depends on the
none of the above
The equivalent resistance of any series of resistors in a circuit is
none of the above
The net charge on a charged capacitor depends on
none of the above
Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is halved, then the force will be
none of the above
Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a
north pole
The end of a compass needle that points to the south pole of a magnet is the
north pole
The conventional direction of magnetic field lines outside a magnet are from
north to south
The unit of electrical resistance is the
ohm
Two charged particles held a certain distance apart are released. As they move, the force on each particle increases. Therefore, their charges have
opposite signs
Modern automobile headlights are connected in
parallel
To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will be least, connect them in
parallel
A beam of electrons can pass through a magnetic field without being deflected if the direction of the beam is
parallel to the field lines
A beam of electrons passing through a magnetic field experiences maximum deflection if the direction of the beam is
perpendicular to the field lines.
The force a magnetic field exerts on a current-carrying wire is maximum when the wire is oriented
perpendicular to the magnetic field.
The force exerted on an electron moving in a magnetic field is maximum when the electron moves
perpendicular to the magnetic field.
Before a thunder storm, clouds in the sky likely become
polarized
The intensity of cosmic rays bombarding the Earth's surface is most at the
poles
If electrons are stripped from an atom it becomes a
positive ion
A negatively-charged rod is held near an aluminum can that rests on a dry wood table. If you momentarily touch the opposite side of the can with your finger, the can becomes
positively charged
One kilowatt is a unit of
power
The brightness of a lamp is directly related to its
power rating
Voltage is most similar to
pressure
If a magnet produces a force on a current-carrying wire, the wire
produces a force on the magnet
Earth's magnetic field is
protective to life on Earth.
Which of these has the greatest mass?
proton
A positive ion has more
protons than electrons
When the distance between two charges is halved, the electrical force between them
quadruples
A main difference between gravitational and electric forces is that electrical forces
repel or attract
Cosmic rays penetrate your body when
safely in your home. in mountainous regions. outdoors.
Two lamps with different filament thicknesses, and therefore different resistances, are connected in series. Greater current is in the lamp with the
same in each
Two charged particles held a certain distance apart are released. As they move, the acceleration of each decreases. Therefore, their charges have
same sign
A transistor is an example of a
semiconductor
The force that acts between a pair of magnetic poles depends on
separation distance. magnetic pole strength.
The force that acts between a pair of electrically-charged particles depends on
separation distance. magnitude of charge.
On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in
series
The safety fuse in an electric circuit is connected to the circuit in
series
To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will increase, connect them in
series
Refrigerator magnets are typically
short range
A capacitor is useful in
smoothing pulsed current
The unit of electric charge, the coulomb, is the charge on a
specific large number of electrons.
Although a magnet can change the direction of travel of an electron beam, it cannot change its
speed kinetic energy.
Magnetism is due to the motion of electrons as they
spin on their axes. move around the nucleus
As the number of loops in a current-carrying wire is increased, the
stronger the enclosed magnetic field.
A superconducting magnet uses
superconducting coils
If both are halved?
the current remains unchanged
What is the effect on the current in a wire if both the voltage across it and its resistance are doubled?
the current remains unchanged
The source of electrons in a simple electric circuit is
the electrical circuit itself.
An iron rod becomes magnetic when
the net spins of many of its electrons are aligned.
The source of energy that illuminates a lamp in your home is
the power company
Although the energy per coulomb of a high-voltage party balloon is high, the energy transfer that occurs if you touch it is low due to
the relatively small amount of charge
Compared with the amount of current in the filament of a lamp, the amount of current in the connecting wires is
the same
Particle A has twice the charge of nearby particle B. Compared to the force on Particle A, the force on Particle B is
the same
The force on an electron moving in a magnetic field will be least when its direction is
the same as the magnetic field direction.
The vast numbers of electrons in a coin don't fly off the surface because
they are attracted by an equal number of protons.
Insulating materials are composed of atoms with
tightly bound outer electrons
Sometimes the current in lamps is too feeble to produce glowing of the lamp filaments, which occurs when
too many lamps are connected in series.
Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts?
touching the light fixture
If an electric toaster rated at 110 V is accidently plugged into a 220-V outlet, the current drawn by the toaster will be
twice its normal value
The electric field between oppositely-charged parallel plates is
uniform
A fundamental rule of electricity is that
unlike kinds of charges attract, like kinds of charges repel
Just as a sustained flow of water in a hydraulic circuit needs a pump, in electric circuits the flow of charge needs
voltage
Just as in hydraulic circuits there is water pressure, in electric circuits there is
voltage
One joule per coulomb is a unit of
voltage
To think of electric potential difference we are thinking about
voltage
The energy dissipated in a light bulb in a circuit is provided by the
voltage source
A lamp rated 23W 120V means that it will deliver 23 W
when the voltage across it is 120 V.
During a lightning strike you don't want to be inside a building framed with
wood
The electric field inside an uncharged metal ball is zero. If the ball is negatively charged, the electric field inside the ball is then
zero
The number of electrons delivered daily to an average American home by an average power utility in the early 21st century was
zero
When a car is struck by lightning, the resulting electric field inside the car is
zero
