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96 Cards in this Set

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Which of the following statements about electric charge are true? (Check all that apply.)
(a) Electric charge is a property of the fundamental particles that make up matter.
(b) There are two types of electric charge, positive and negative.
(c) All objects are electrically charged.
(d) Electric charge cannot be created or destroyed.
(e) Most macroscopic objects are charged by transferring protons from one object to another.
(f) Metals are the best electrical conductors for the same reason they are the best thermal conductors.
(a) Electric charge is a property of the fundamental particles that make up matter.
(b) There are two types of electric charge, positive and negative.
(d) Electric charge cannot be created or destroyed.
(f) Metals are the best electrical conductors for the same reason they are the best thermal conductors.
A positively charged rod attracts a small, uncharged piece of paper. A negatively charged rod will
(a) repel a small, uncharged piece of paper.
(b) attract a small, uncharged piece of paper.
(c) neither attract nor repel a small, uncharged piece of paper.
(b) attract a small, uncharged piece of paper
Which of the following describe the force between two positively charged particles? (Check all that apply.)
(a) The direction of the force on particle 1 is away from particle 2.
(b) The direction of the force on particle 1 is toward particle 2.
(c) The magnitude of the force on particle 1 depends on the magnitude of the charge on particle 2 but not on the magnitude of the charge on particle 1.
(d) The magnitude of the force on particle 1 depends on the magnitude of the charge on particle 2 and the magnitude of the charge on particle 1.
(e) The magnitude of the force on particle 2 is directly proportional to the square of the distance between the charges.
(f) The magnitude of the force on particle 2 is inversely proportional to the square of the distance between the charges.
(a) The direction of the force on particle 1 is away from particle 2.
(d) The magnitude of the force on particle 1 depends on the magnitude of the charge on particle 2 and the magnitude of the charge on particle 1.
(f) The magnitude of the force on particle 2 is inversely proportional to the square of the distance between the charges.
How can it be determined if there is a nonzero electric field at a point in space?
(a) Determine if there are any charges around that could produce an electric field.
(b) Place a test charge at that point. If there is a force on the test charge then there is a nonzero electric field at that point.
(c) Place a test charge at that point. If there is an electric force on the test charge then there is a nonzero electric field at that point.
(d) It can't be determined because the direction of the electric field depends on whether the test charge is positive or negative.
(c) Place a test charge at that point. If there is an electric force on the test charge then there is a nonzero electric field at that point.
At a point in space there is an electric field that points south. What is the direction of the force on a charge placed at that point?
(a) North, regardless of the sign of the charge.
(b) South, regardless of the sign of the charge.
(c) North if the charge is positive and south if the charge is negative.
(d) South if the charge is positive and north if the charge is negative.
(d) South if the charge is positive and north if the charge is negative.
When a positive charge is placed at a point in space there is an electric force on it toward the south. What is the direction of the electric field at that point?
(a) North, regardless of the sign of the charge.
(b) South, regardless of the sign of the charge.
(c) North if the charge is positive and south if the charge is negative.
(d) South if the charge is positive and north if the charge is negative.
(b) South, regardless of the sign on the charge
A solid metal sphere is given a positive charge. Which of the following statements is true?
(a) The charge is distributed throughout the volume of the sphere and there is a nonzero electrostatic field inside the sphere.
(b) The charge is distributed throughout the volume of the sphere and the electrostatic field inside the sphere is zero.
(c) The charge is on the surface of the sphere and there is a nonzero electric field inside the sphere.
(d) The charge is on the surface of the sphere and the electric field inside the sphere is zero.
(d) The charge is on the surface of the sphere and the electric field inside the sphere is zero.
Why must electrostatic field lines be perpendicular to the surface of a conductor?
(a) If they weren't perpendicular then electrons in the conductor would move.
(b) If they weren't perpendicular then the electric flux through the surface would be zero.
(c) Because the electric field inside a conductor is zero.
(d) Because the charge on a conductor is on the surface.
(a) If they weren't perpendicular then electrons in the conductor would move.
Which of the following is a statement of Gauss' law?
(a) Electric flux is proportional to electric charge.
(b) The electric flux through a surface is proportional to the charge on the surface.
(c) The electric flux through a closed surface is proportional to the charge enclosed by the surface.
(d) The electric flux through a surface is the product of the perpendicular component of the electric field through the surface and the surface area.
(c) The electric flux through a closed surface is proportional to the charge enclosed by the surface.
A proton is placed near the positive plate of a parallel plate capacitor and an electron is placed the same distance from the negative plate. Which of the following statements are true? (Check all that apply.)
(a) The proton has high electric potential energy.
(b) The proton has low electric potential energy.
(c) The point where the proton is has high electric potential.
(d) The point where the proton is has low electric potential.
(e) The electron has high electric potential energy.
(f) The electron has low electric potential energy.
(g) The point where the electron is has high electric potential.
(h) The point where the electron is has low electric potential.
(a) The proton has high electric potential energy.
(c) The point where the proton is has high electric potential.
(e) The electron has high electric potential energy.
(h) The point where the electron is has low electric potential.
Which of the following best describes what is meant by saying a capacitor has a charge Q?
(a) The net charge on the capacitor is Q.
(b) The charge on the positive plate of the capacitor is Q. The charge on the other plate is zero.
(c) The charge on the negative plate of the capacitor is –Q. The charge on the other plate is zero.
(d) The charge on the positive plate of the capacitor is Q. The charge on the negative plate is –Q. The net charge of the capacitor is zero.
(d) The charge on the positive plate of the capacitor is Q. The charge on the negative plate is –Q. The net charge of the capacitor is zero.
Why does placing a dielectric between the plates of a capacitor increase its capacitance?
(a) The dielectric becomes polarized, decreasing the electric field and the potential difference between the plates.
(b) The dielectric becomes polarized, increasing the charge on the capacitor.
(c) The dielectric transfers charge onto the plates of the capacitor.
(d) The dielectric increases the potential difference between the plates of the capacitor.
(a) The dielectric becomes polarized, decreasing the electric field and the potential difference between the plates.
A capacitor is charged by connecting it to a battery. It is then disconnected from the battery and connected to an uncharged capacitor. What, if anything, must be the same for the system of the two connected capacitors as for the single capacitor connected to the battery?
(a) The potential difference.
(b) The charge on the original capacitor.
(c) The total charge on the capacitors.
(d) Nothing.
(c) The total charge on the capacitors.
What is the purpose of a battery in an electric circuit?
(a) A battery supplies electric charge to the circuit.
(b) A battery supplies electric energy to the circuit.
(c) A battery supplies electric current to the circuit
Both (a) and (b).
All of the above.
(b) A battery supplies electric energy to the circuit
What is the direction of the conventional electric current in a circuit? (Check all that apply.) (a) From high potential to low potential.
(b) From low potential to high potential.
(c) From positive to negative.
(d) From negative to positive.
(e) The direction that electrons move through the circuit.
(f) Opposite the direction that electrons move through the circuit.
(a) From high potential to low potential.
(c) From positive to negative.
(f) Opposite the direction that electrons move through the circuit.
Which of the following is the best statement of Ohm's law?
(a) The current in a metal wire is proportional to the potential difference applied to its two ends.
(b) The resistance of any circuit element is equal to the voltage across it divided by the current through it.
(c) The voltage across any circuit element is equal to the current through it times its resistance.
(a) The current in a metal wire is proportional to the potential difference applied to its two ends.
The resistance of a wire depends on which of the following? (Check all that apply.)
(a) The length of the wire.
(b) The thickness of the wire.
(c) The material from which the wire is made.
(d) The temperature of the wire.
(e) The potential difference across the ends of a wire.
(a) The length of the wire.
(b) The thickness of the wire.
(c) The material from which the wire is made.
(d) The temperature of the wire.
What is electric power?
(a) The rate at which electrical energy is changed to some other type of energy.
(b) The rate at which some other type of energy is changed to electrical energy.
Both (a) and (b).
None of the above.
Both (a) and (b)
A step-up transformer: (check all that apply)
(a) steps up current.
(b) steps down current.
(c) steps up voltage.
(d) steps down voltage.
(e) has more turns in its primary than in its secondary.
(f) has more turns in its secondary than in its primary.
(b) steps down current.
(c) steps up voltage.
(f) has more turns in its secondary than in its primary.
What is the main reason that electric power is transmitted at high voltage?
(a) Generators produce power at high voltage.
(b) Consumers use power at high voltage.
(c) High voltage means low current and smaller resistive power losses.
(d) High voltage means high current and high power.
(c) High voltage means low current and smaller resistive power losses.
The induced emf in a coil depends on which of the following? (Check all that apply.)
(a) The inductance of the coil.
(b) The resistance of the coil.
(c) The rate of change of current in the coil.
(d) Whether the current is increasing or decreasing.
(a) The inductance of the coil.
(c) The rate of change of current in the coil.
(d) Whether the current is increasing or decreasing.
A simple ac generator consists of a coil of wire rotating in a uniform magnetic field. The peak output of the generator depends on which of the following? (Check all that apply.)
(a) The magnitude of the magnetic field.
(b) The rate at which the coil is rotated.
(c) The number of loops of wire in the coil.
(d) The angle the coil makes with the magnetic field.
(a) The magnitude of the magnetic field.
(b) The rate at which the coil is rotated.
(c) The number of loops of wire in the coil.
When a motor is running it is also generating an emf

True or False?
True
The torque produced by the current in a generator is always opposite to the torque turning the generator

True or False
True
A metal rod in a uniform magnetic field slides on a U-shaped conductor, as shown in the diagram. Check all that apply
(a) There is an induced emf because the magnetic flux is changing as the rod moves
(b) as the rod moves the magnetic flux increases because the magnetic field decreases
(c) As the rod moves the magnetic flux increases because the area increases
(d) There is a magnetic force in the electrons in the rod
(e) The induced emf equals the work done by the magnetic force per unit charge
(f) There is an induced electric field in the rod
(g) The induced current is clockwise
(h) The induced current is counterclockwise
(a) There is an induced emf because the magnetic flux is changing as the rod moves
(c) As the rod moves the magnetic flux increases because the area increases
(d) There is a magnetic force in the electrons in the rod
(e) The induced emf equals the work done by the magnetic force per unit charge
(f) There is an induced electric field in the rod
(g) The induced current is clockwise
A coil of wire is connected to a galvanometer. In which of the following situations will a current be induced in the coil? (check all that apply)
(a) A bar magnet moves towards the coil
(b) A bar magnet moves away from the coil
(c) A bar magnet is at rest in the coil
(d) There is a constant magnetic flux through the coil
(e) There is a changing magnetic flux through the coil
(f) The coil is rotated in a uniform magnetic field
(g) There is a steady current in a second coil near the first coil
(h) There is a changing current in a second coil near the first coil
(a) A bar magnet moves towards the coil
(b) A bar magnet moves away from the coil
(e) There is a changing magnetic flux through the coil
(f) The coil is rotated in a uniform magnetic field
(h) There is a changing current in a second coil near the first coil
When is Ampere's law valid?
(a) Always
(b) Only for current carrying wires
(c) Only for situations where the currents and fields are not changing in time
(d) Only for simple or symmetric situations
(c) Only for situations where the currents and fields are not changing in time
A flat, current carrying coil of wire is in a uniform magnetic field. When is the torque on the coil maximum?
(a) When the plane of the coil is parallel to the magnetic field
(b) When the plane of the coil is perpendicular to the magnetic field
(c) When the normal to the plane of the coil makes an angle of 45 with the plane of the field
(d) The torque on the coil is constant
(a) When the plane of the coil is parallel to the magnetic field
What is the purpose of a commutator in a dc motor?
(a) The change the direction of the current around the coil so the direction of the torque remains the same
(b) The change the direction of the torque so the direction of the current around the coil remains the same
(c) To change electrical energy into mechanical energy
(d) To change mechanical energy into electrical energy
(a) The change the direction of the current around the coil so the direction of the torque remains the same
What is the path of a charged particle with velocity perpendicular to a magnetic field? Assume the particle remains within the field at all times. Neglect gravity and assume that the electric field is zero.
(a) A straight line
(b) A circle whose radius is directly proportional to the magnitude of the magnetic field
(c) A circle whose radius is inversely proportional to the magnitude of the magnetic field
(d) A helix
(c) A circle whose radius is inversely proportional to the magnitude of the magnetic field
The magnetic field produced by a long, straight, current carrying wire is
(a) uniform
(b) directly proportional to the current and inversely proportional to the distance from the wire
(c) inversely proportional to the current and directly proportional to the distance from the wire
(d) proportional to the current and independent of the distance from the wire
(b) directly proportional to the current and inversely proportional to the distance from the wire
A loop of wire carries a clockwise current. The direction of the magnetic field at the center of the loop is
(a) in
(b) out
(c) clockwise
(d) counterclockwise
(a) in
Which of the following objects are magnetic?
(a) a steel paper clip
(b) a sheet of paper
(c) an iron nail
(d) a compass needle
(e) the earth
(f) a wooden pencil
they are all magnetic
What is the direction of the force on an electron moving to the right in a uniform magnetic field directed inwards?
(a) up
(b) down
(c) left
(d) right
(e) in
(f) out
(b) down
What is the direction of the force on a wire carrying a downwards current in a uniform magnetic field directed to the right?
(a) up
(b) down
(c) left
(d) in
(e) out
(e) out
Which of the following statements is true for capacitors in series?
(a) the potential difference must be the same across each capacitor
(b) the charge must be the same on each capacitor
(c) the equivalent capacitance equals the sum of the individual capacitances
(d) the voltage is greatest across the one with the highest capacitance
(b) the charge must be the same on each capacitor
A fully charged capacitor is connected to a resistor and a switch which is initially open. When the switch is closed
(a) the current remains zero
(b) the current increases exponentially
(c) the current decreases exponentially
(d) the capacitor discharges instantaneously
(c) the current decreases exponentially
A circuit consists of an ideal 6 V battery, a 2 Ω resistor and a 4 Ω resistor in series. How should a voltmeter be connected to measure the voltage across the 2 Ω resistor?
(a) In parallel with the 2 Ω resistor.
(b) In series with the 2 Ω resistor.
(c) In parallel with the battery.
(d) In series with the battery.
(e) It doesn't matter because the current is the same for all the circuit elements.
(a) In parallel with the 2 Ω resistor.
Which of the following statements must be true for any circuit? (Check all that apply.)
(a) The voltage is the same across all the branches in the circuit.
(b) The voltage is different across all the branches in the circuit.
(c) The current is the same everywhere in a branch.
(d) The voltage is the same everywhere in a branch.
(e) At any junction, the total current into the junction equals the total current out of the
junction.
(f) The total change in potential around any closed path of the circuit is zero.
(g) The direction of the current through any circuit element is from high potential to low potential.
(h) The direction of the current through a resistor is from high potential to low potential.
(c) The current is the same everywhere in a branch.
(e) At any junction, the total current into the junction equals the total current out of the
junction.
(f) The total change in potential around any closed path of the circuit is zero.
(h) The direction of the current through a resistor is from high potential to low potential
A circuit consists of two real batteries, one with an emf of 18 V and the other with an emf of 12 V and ideal connecting wires. The positive terminals of the batteries are connected directly and their negative terminals are also connected directly. Which of the following statements are true about the batteries? (Check all that apply.)
Hint: draw the circuit diagram.
(a) The current is the same through both batteries.
(b) The terminal voltage is the same for both batteries.
(c) The terminal voltage is 18 V.
(d) The terminal voltage is 12 V.
(e) The terminal voltage is between 12 V and 18 V.
(f) The 12 V battery is charging and the 18 V battery is discharging.
(h) The 18 V battery is charging and the 12 V battery is discharging.
(a) The current is the same through both batteries.
(b) The terminal voltage is the same for both batteries.
(e) The terminal voltage is between 12 V and 18 V.
(f) The 12 V battery is charging and the 18 V battery is discharging.
Which of the following are necessarily true about resistors in series? (Check all that apply.)
(a) The current is the same through each resistor.
(b) The potential difference (voltage) is the same across each resistor.
(c) All the resistors are in the same branch of the circuit.
(d) Each resistor is in a different branch of the circuit.
(e) The total current equals the sum of the currents through each resistor.
(f) The total voltage equals the sum of the voltages across each resistor.
(a) The current is the same through each resistor.
(c) All the resistors are in the same branch of the circuit.
(f) The total voltage equals the sum of the voltages across each resistor.
Which of the following are necessarily true about resistors in parallel? (Check all that apply.)
(a) The current is the same through each resistor.
(b) The potential difference (voltage) is the same across each resistor.
(c) All the resistors are in the same branch of the circuit.
(d) Each resistor is in a different branch of the circuit.
(e) The total current equals the sum of the currents through each resistor.
(f) The total voltage equals the sum of the voltages across each resistor.
(b) The potential difference (voltage) is the same across each resistor.
(d) Each resistor is in a different branch of the circuit.
(e) The total current equals the sum of the currents through each resistor.
When is the potential difference of a real battery equal to its emf?
(a) Always.
(b) When the battery is fully charged.
(c) When there is no current through the battery.
(d) Never.
(c) When there is no current through the battery
What is the main reason that the terminal voltage of a battery is not independent of the current in the circuit?
(a) A real battery has internal resistance.
(b) Real wires have resistance.
(c) The terminal voltage of a real battery is not equal to its emf.
(d) The emf of a real battery is not constant.
(a) A real battery has internal resistance.
A real battery has an emf of 6 V and an internal resistance of 1 Ω. What is the terminal voltage of the battery when it has its maximum possible current through it?
(a) zero
(b) less than 6 V but not zero
(c) 6 V
(d) greater than 6 V
(a) zero
Below the critical temperature the resistivity of a superconductor
(a) approaches zero as the temperature approaches absolute zero
(b) approaches a minimum nonzero value as the temperature approaches absolute zero
(c) is linear with temperature
(d) is approximately zero
(e) is exactly zero
(e) is exactly zero
For capacitors in parallel
(a) the current is the same everywhere in a branch of the circuit
(b) the voltage is the same across all branches in the circuit
(c) the direction of the current through a resistor is from low potential to high potential
(d) both (a) and (b)
(e) All of the above
(a) the current is the same everywhere in a branch of a circuit
When is the potential difference of a real battery equal to its emf?
(a) Always
(b) When the battery is fully charged
(c) When the terminals of the battery are short circuited
(d) When there is no current through the battery
(e) Never
(d) when there is no current through the battery
A circuit consists of an ideal 12 V battery, a 4 ohm resistor and a 6 ohm resistor in parallel. How should an ammeter be connected to measure the current through the 4 ohm resistor?
(a) in series with the 4 ohm resistor
(b) in parallel with the 4 ohm resistor
(c) in series with the battery
(d) it doesnt matter since the current is the same for all circuit elements
(e) it doesnt matter since the voltage is the same for all circuit elements
(a) in series with the 4 ohm resistor
A flat, current carrying coil of water is in a uniform magnetic field. When is the torque on the coil zero?
(a) when the plane of the coil is perpendicular to the magnetic field
(b) when the plane of the coil is parallel to the magnetic field
(c) when the plane of the coil makes a 45 degree angle to the magnetic field
(d) when the normal to the plane of the coil is perpendicular to the magnetic field
(e) the torque is never zero
(a) when the plane of the coil is perpendicular to the magnetic field
What is the main difference between direct current (dc) and alternating current (ac)?
(a) Direct current is constant; alternating current is sinusoidal
(b) The direction of the current doesn't change in direct current; the current periodically reverses direction in alternating current
(c) Direct current is produced by batteries; alternating current by generators
(d) Ohm's law only applies to direct current, not alternating current
(b) The direction of the current doesn't change in direct current; the current periodically reverses direction in alternating current
What is the advantage of using the rms values of current and voltage? (check all that apply)
(a) For circuits containing only resistive elements, using the rms values allows us to use the same equations for AC circuits as for DC circuits
(b) The rms values are easier to calculate that the peak values
(c) The rms values are easier to calculate that the average (mean) values
(d) The rms values are not zero while the average values are zero
(a) For circuits containing only resistive elements, using the rms values allows us to use the same equations for AC circuits as for DC circuits
(d) The rms values are not zero while the average values are zero
When is the potential difference of a real battery equal to its emf?
(a) Always
(b) When the batter is fully charged
(c) When there is no current through the battery
(d) Never
(c) When there is no current through the battery
What is the main reason that the terminal voltage of a battery is not independent of the current in the circuit?
(a) A real battery has internal resistance
(b) Real wires have resistance
(c) The terminal voltage of a real battery is not equal to its emf
(d) The emf of a real battery is not constant
(a) A real battery has internal resistance
A Real battery has an emf of 6 V and an internal resistance of 1 Ω. What is the terminal voltage of the battery when it has its maximum possible current through it?
(a) zero
(b) less than 6 V but not zero
(c) 6 V
(d) greater than 6 V
(a) zero
A coil of wire has both inductance ans resistance. It is connected through a switch to an ideal battery. The switch is initially open and there is no current in the coil. What happens when the switch is closed?
(a) The current remains zero
(B) The current instantly reaches its maximum value
(c) The current starts out at its maximum value and decreases, approaching zero asymptotically
(d) The current starts out at zero and increases, approaching its maximum value asymptotically
(d) The current starts out at zero and increases, approaching its maximum value asymptotically
Match the phase relationship or frequency dependance of reactance with he type of circuit element.
( ) current lags voltage
( ) current leads voltage
( ) phase of current and voltage are the same
( ) reactance is proportional it frequency
( ) reactance is inversely proportional to frequency

A. capacitor
B. inductor
C. resistor
(b) current lags voltage
(a) current leads voltage
(c) phase of current and voltage are the same
(b) reactance is proportional it frequency
(a) reactance is inversely proportional to frequency
Consider a series circuit containing an inductor L, a resistor R, and a capacitor C connected to a variable frequency ac source. Which of the following statements are correct? (check all that apply)
(a) The peak voltage across the source equals the peak voltage across the capacitor plus the peak voltage across the resistor plus the peak voltage across the inductor
(b) At any instant, the voltage across the inductor equals the current times the inductive reactance
(c) The rms current in the circuit equals the rms voltage of the source divided by the impedance of the circuit
(d) As resonance the current through the circuit is in phase with the voltage of the source
(e) The impedance of the circuit is independent of the frequency of the source
(f) The voltage across the inductor is 180º out of phase with the voltage across the capacitor
(b) At any instant, the voltage across the inductor equals the current times the inductive reactance
(c) The rms current in the circuit equals the rms voltage of the source divided by the impedance of the circuit
(d) As resonance the current through the circuit is in phase with the voltage of the source
(f) The voltage across the inductor is 180º out of phase with the voltage across the capacitor
Name that solid:
partially filled conduction band
metal (conductor)
Name that solid:
filled valence band; empty conduction band; small energy gap
semiconductor
Name that solid:
filled valence band; empty conduction band; large energy gap
insulator
What carries the electric current in a p-type semiconductor?
(a) electrons
(b) protons
(c) positively charged holes
(d) negatively charged holes
(c) positively charged holes
According to Maxwell's equations, how are magnetic fields produced? (Check all that apply)
(a) By electric charges (moving or not)
(b) By moving electric charges (electric currents)
(c) By changing electric fields
(d) By changing magnetic fields
(b) By moving electric charges (electric currents)
(c) By changing electric fields
How are electromagnetic waves produced?
(a) By electric charges
(b) By magnets
(c) By moving electric charges
(d) By accelerating electric charges
(d) By accelerating electric charges
How does a loop antenna detect an electromagnetic wave?
(a) the magnetic field of the wave produces an electric current in the antenna
(b) The changing magnetic field of the wave induces an electric current in the antenna
(c) The electric field if the wave produces an electric current in the antenna
(d) The changing electric field of the wave induces an electric current in the antenna
(b) The changing magnetic field of the wave induces an electric current in the antenna
How does a loop antenna detect an electromagnetic?
(a) The magnetic field of the wave produces an electric current in the antenna
(b) The changing magnetic field of the wave induces an electric current in the antenna
(c) The electric field of the wave produces an electric current in the antenna
(d) The changing electric field of the eave induces an electric current in the antenna
(b) The changing magnetic field of the wave induces an electric current in the antenna
According to the theory of relativity, everything is relative.

True or False?
False
A spaceship traveling at half the speed of light (o.5c) relative to an observer on Earth fires a laser cannon in the forward direction. The observer on Earth measures the speed of light from the laser cannon as:
(a) 0.5c
(b) c
(c) 1.5c
(d) 2c
(b) c
Which of the following are consequences of the postulates of special relativity? (check all that apply)
(a) Two events happen at the same time in one frame of reference don't necessarily happen at the same time according to observers in a different frame of reference
(b) An even that causes a second event in one frame of reference doesn't necessarily cause the second event according to observers in a different frame of reference
(c) Time is absolute
(d) Moving clocks run slow
(e) The length of a moving object is contracted in all directions
(f) Mass is a form of energy
(a) Two events happen at the same time in one frame of reference don't necessarily happen at the same time according to observers in a different frame of reference
(d) Moving clocks run slow
(f) Mass is a form of energy
According to the correspondence principle:
(a) classical mechanics must be replaced by relativity
(b) classical mechanics is a more general theory than relativity
(c) classical mechanics is a limiting case of relativity
(d) classical mechanics corresponds with special relativity
(c) classical mechanics is a limiting case of relativity
According to the principle of equivalence
(a) gravity and acceleration are the same thing
(b) a gravitational field and a uniform acceleration are the same thing
(c) a uniform gravitational field and a uniform acceleration are the same thing
(d) no experiment can distinguish between a uniform gravitational field and an equivalent uniform acceleration
(d) no experiment can distinguish between a uniform gravitational field and an equivalent uniform acceleration
Which of the following are consequences of the principle of equivalence? (check all the apply)
(a) bending of light by gravity
(b) curvature of space-time
(c) gravitational redshift
(d) gravitational waves
(e) black holes
(f) A clock at the bottom of the Empire State building runs slower than an identical clock at the top of the Empire State building
(a) bending of light by gravity
(b) curvature of space-time
(c) gravitational redshift
(d) gravitational waves
(e) black holes
(f) A clock at the bottom of the Empire State building runs slower than an identical clock at the top of the Empire State building
Why does a shirt or blouse taken from a clothes dryer sometimes cling to your body?
The shirt or blouse becomes electrically charged by friction while tumbling in the dryer. The charged garment induces a charge on your body which results in a net attractive force between the garment and your body causing "static cling"
What is electrical potential energy?
The electrical potential energy of a system equals the work done in assembling the system i.e. 9 J
When a flashlight is operated, what is being used up: battery current, battery voltage, battery energy, or battery power? Explain for each one why it is or isn't used up.
Battery energy is the only one that isn't "used up," in the sense that chemical energy stored in the battery is changed to electrical energy which is then changed to thermal energy and light by the flashlight bulb. The amount of chemical energy in the battery decreases as the flashlight is operated. The voltage of the battery remains nearly constant. The power of the batter is the rate at which chemical energy is changed to electrical energy.
When a "short circuit" occurs in a device, the electrical resistance of the device decreases (sometimes drastically). Describe in words what you think a "short circuit" is. What could happen inside an appliance that would reduce its electrical resistance?
A short circuit results when electrons are somehow allowed to pass AROUND a source of resistance instead of THROUGH it.
For example, if the insulation around two wires wears away, the wires might touch each other and allow current to pass from one to the other, skipping a lot of the resistive elements in the circuit. This results in an increase in electric current, sometimes enough to overload the circuit.
Suppose that your toaster over has a short circuit in it so that its resistance suddenly becomes 1/4 of its original value. Now what will happen in your household circuit?
Because resistance is decreasing and voltage remains the same, current in the circuit has increased passed the circuit breaker's ability and the circuit is shorted.
What does the resistance of a wire depend on?
The material it is made out of, its length and cross sectional area
The heating element of a toaster is made of Nichrome wire. Immediately after the toaster is turned on, is the rms current in the wire increasing, decreasing, or staying constant?
As the wire heats up its resistance increases so the rms current decreases
An incandescent light bulb is most likely to burn out when it is first turned on. Why?
When the light bulb is first turned on its filament is cold and has its lowest resistance. Therefore the current through the bulb and the power the bulb must dissipate is largest when it is first turned on so it is more likely to burn out then than after it has been on for awhile and the filament's temperature and resistance are higher
Explain why the voltage across a resistor is not the same as the voltage of a battery
A resistor is connected across the terminals of a battery so the voltage across the resistor equals the terminal voltage of the battery which is less than the emf since there is current in the circuit
Explain why the voltage across a resistor equals the terminal voltage of a battery
The resistor is connected across the terminals of the battery
The voltage across resistors in parallel is _______.
the same
An electron is released from rest in a strong, constant magnetic field. What happens to the electron?
The electron will remain at rest since it will not experience a force. In order for an electron, or any charged particle, to experience a force due to a magnetic field, that particle must be moving across magnetic field lines.
A positively charged ion is moving horizontally to the right when it feels a downward force and begins to move in a curved trajectory. Determine the direction of the electric field that could cause the ion to feel such a downward force, and then determine the direction of the magnetic field that could cause it. Indicate your answers with a sketch.
If this downward force results from an electric field, then the electric field points towards the bottom of the page. If the force on the particle results from a magnetic field, then the magnetic field must lie in the plane that is perpendicular to the page and contains the velocity vector; also the magnetic field must have a component pointing out of the page (an example of this is a magnetic field that is pointing directly out of the page)
In Faraday's law, what is the meaning of the negative sign?
The negative sign tells us that the induced emf is opposite in sense to the rate of change of flux, in agreement with Lenz's law
Why won't a transformer work with a constant DC source?
For a constant DC source the current through the primary is constant so the magnetic flux through the secondary coil is also constant and there is no induced emf in the secondary
If AC current can be produced with a magnet and a wire loop, why don't we get pollution-free energy this way?
The question is, how do we turn the loop of the wire? That's what the coal, natural gas, nuclear energy, etc. are used for in a power plant
Explain why there is an induced voltage in an inductor
The changing current in the coil produces a changing magnetic flux through the coil so there is an induced voltage in the coil
Explain why the sum of the rms voltages across each circuit element does not equal the rms voltage
The voltages across the circuit elements are out of phase with each other
Describe briefly how the frequency of the source emf affects the impedance of
(a) a pure resistance
(b) a pure capacitance
(c) a pure inductance
(d) an LRC circuit near resonance (R small)
In which case is the impedance zero for zero frequency (ie direct current)? In which case is the current zero for zero frequency?
(a) The impedance of a pure resistance is independent of the frequency of the source (Z=R)
(b) The impedance of a pure capacitance is inversely proportional to the frequency of the source
(c) The impedance of a pure inductance is directly proportional to the frequency of the source
(d) The impedance of an LRC circuit is very sensitive to frequency near resonance. At resonance the impedance has it minimum value and it increases rapidly as the source frequency either increases or decreases
(e) The zero frequency impedance is zero for a pure inductance. The zero frequency is zero for pure capacitance
Which device (the inductor, resistor, or capacitor) in an LRC circuit dominates the impedance at
(a) very low frequency
(b) very high frequency
(c) near resonant frequency
(a) The capacitor since its reactance is very high at very low frequency
(b) The inductor since its reactance is very high at very high frequency
(c) The resistance since near resonance the reactances of the inductor and capacitor are nearly equal
At what frequency of the source will the rms current in the circuit be maximum?
The current is maximum at resonance
Decide whether an electric field, a magnetic field, and/or electromagnetic waves will be produced

(a) A point charge moving at a constant speed in a circle
(b) A constant current in a straight wire
(a) A point charge moving at a constant speed in a circle is accelerating and therefore produces electromagnetic waves. An electromagnetic wave is composed of electric and magnetic fields.
(b) A constant current in a straight wire produces a magnetic field since the current is due to moving charges. However the net charge is zero so there is no electric field
A metal rid moves at constant speed in a magnetic field. Which of the following statement is(are) correct?
(a) There is a magnetic force on the electrons in the rod
(b) There is an emf induced across the rod
(c) There is an induced electric field in the rod
(d) Both (a) and (b)
(e) All of the above
(e) All of the above
How does a negatively charged rid attracts a small, uncharged piece of paper?
(a) The rod induces a net negative charge on the paper. Like charges attract
(b) The rod induces a net positive charge on the paper. Unlike charges attract
(c) The rod polarizes the molecules in the paper. The side of the paper nearest the rod becomes positively charged and the opposite side becomes negatively charged. There is a net attraction
(e) The rod can't attract the paper since the paper is uncharged
(c) The rod polarizes the molecules in the paper. The side of the paper nearest the rod becomes negatively charged. There is a net attraction