Question 1

A device used chiefly for storing energy in a magnetic field is

Accepted Answer

A)  an inductor. 
B)  a resistor. 
C)  a capacitor. 
D)  a galvanometer. 
E)  a dielectric. 
A)  an inductor. 
B)  a resistor. 
C)  a capacitor. 
D)  a galvanometer. 
E)  a dielectric.

Question 2

An LR circuit has a resistance R = 25  $\Omega$ , an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved?

Accepted Answer

A)  zero 
B)  0.35 J 
C)  0.35 mJ 
D)  0.70 mJ 
E)  0.97 mJ 
A)  zero 
B)  0.35 J 
C)  0.35 mJ 
D)  0.70 mJ 
E)  0.97 mJ

Question 3

A circular loop of radius 25 cm is sitting in a perpendicular magnetic field of 0.2 T. If the magnetic field strength changes to a value of 0.5 T in 2.5 s, calculate the induced EMF in the loop.

Accepted Answer

A)  7.5 * 10-3 V 
B)  9.6 * 10-2 V 
C)  4.0 * 10-2 V 
D)  2.4*10-2 V 
E)  none of the above 
A)  7.5 * 10-3 V 
B)  9.6 * 10-2 V 
C)  4.0 * 10-2 V 
D)  2.4*10-2 V 
E)  none of the above

Question 4

Use the following figure for the next three problems.  
-A rectangular coil moving at a constant speed v enters a region of uniform magnetic field from the left. While the coil is exiting the field on the right, the direction of the magnetic force is

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 5

You place a single loop of wire 0.50 m by 0.30 m perpendicular to a field of 2.0 T. In 30 ms you turn the loop until it is parallel with the field. The average emf induced in this loop is

Accepted Answer

A)  0.30 V 
B)  10 V 
C)  5.0 V 
D)  67 V 
E)  20 V 
A)  0.30 V 
B)  10 V 
C)  5.0 V 
D)  67 V 
E)  20 V

Question 6

Which law does the following statement express? "In all cases of electromagnetic induction, the induced voltages have a direction such that the currents they produce oppose the effect that produces them."

Accepted Answer

A)  Maxwell's law 
B)  Fleming's rule 
C)  Lenz's law 
D)  Gauss's law 
E)  Ampère's law 
A)  Maxwell's law 
B)  Fleming's rule 
C)  Lenz's law 
D)  Gauss's law 
E)  Ampère's law

Question 7

A wire rod rolls with a speed of 30 m/s on two metallic rails, 2.0 m apart, that form a closed loop. The power dissipated in the resistor R and the current direction are, respectively,

Accepted Answer

A)  33 mW, clockwise. 
B)  33 mW, counterclockwise. 
C)  2.0 W, counterclockwise. 
D)  10 W, clockwise. 
E)  10 W, counterclockwise. 
A)  33 mW, clockwise. 
B)  33 mW, counterclockwise. 
C)  2.0 W, counterclockwise. 
D)  10 W, clockwise. 
E)  10 W, counterclockwise.

Question 8

Use the following figure for the next two problems:  
-A classic demonstration illustrating eddy currents is performed by dropping a permanent magnet inside a conducting cylinder. The magnet does not go into free fall. Instead it reaches terminal velocity and can take a few seconds to drop a length of about a meter. Suppose the mass of the magnet is 70 g and width of 1.0 cm. It falls with a terminal velocity of 10 cm/s and the length of the pipe is 80 cm. The magnitude of the Joule heating from the eddy currents is approximately

Accepted Answer

A)  0.55 J 
B)  8.8 * 10-5 J 
C)  1.1 J 
D)  1.8 *10-4 J 
E)  None of these is correct. 
A)  0.55 J 
B)  8.8 * 10-5 J 
C)  1.1 J 
D)  1.8 *10-4 J 
E)  None of these is correct.

Question 9

The magnetic flux through a loop is made to vary according to the relation
$\phi$m = 6t2 + 7t + 1
Where the units are SI. The EMF induced in the loop when t = 2 s is

Accepted Answer

A)  38 V 
B)  39 V 
C)  40 V 
D)  31 V 
E)  19 V 
A)  38 V 
B)  39 V 
C)  40 V 
D)  31 V 
E)  19 V

Question 10

The plane of a circular, 200-turn coil of radius 5.25 cm is perpendicular to a uniform magnetic field produced by a large electromagnet. This field is changed at a steady rate from 0.650 T to 0.150 T in 0.0100 s. What is the magnitude of the EMF induced in the coil?

Accepted Answer

A)  110 V 
B)  170 V 
C)  1.7 V 
D)  26 V 
E)  87 V 
A)  110 V 
B)  170 V 
C)  1.7 V 
D)  26 V 
E)  87 V

Question 11

How much does the energy stored in an inductor change if the current through the inductor is doubled?

Accepted Answer

A)  it is the same 
B)  it is doubled 
C)  it is quadrupled 
D)  it is halved 
E)  it is quartered 
A)  it is the same 
B)  it is doubled 
C)  it is quadrupled 
D)  it is halved 
E)  it is quartered

Question 12

Suppose you double the magnetic field in a given region and quadruple the area through which this magnetic field exists. The effect on the flux through this area would be to

Accepted Answer

A)  leave it unchanged. 
B)  double it. 
C)  quadruple it. 
D)  increase it by a factor of six. 
E)  increase it by a factor of eight. 
A)  leave it unchanged. 
B)  double it. 
C)  quadruple it. 
D)  increase it by a factor of six. 
E)  increase it by a factor of eight.

Question 13

The current in an RL circuit is zero at time t = 0 and increases to 75% of its final value in 4.5 s. The time constant of this circuit is approximately

Accepted Answer

A)  6.0 s 
B)  12 s 
C)  8.7 s 
D)  3.3 s 
E)  9.8 s 
A)  6.0 s 
B)  12 s 
C)  8.7 s 
D)  3.3 s 
E)  9.8 s

Question 14

A region of space contains a magnetic field of 500 G and an electric field of
3 *106 N/C. The total energy density in a cubical box of side   = 20 cm in this region is

Accepted Answer

A)  19.4 kJ/m3  
B)  12.2 kJ/m3  
C)  1.03 kJ/m3  
D)  66.9 J/m3  
E)  24.6 J/m3  
A)  19.4 kJ/m3  
B)  12.2 kJ/m3  
C)  1.03 kJ/m3  
D)  66.9 J/m3  
E)  24.6 J/m3

Question 15

The magnetic flux through a certain coil is given by
$\phi$m = (1/50 $\pi$) cos 100 $\pi$t
Where the units are SI. The coil has 100 turns. The magnitude of the induced EMF when t = 1/200 s is

Accepted Answer

A)  100 V 
B)  200 V 
C)  zero 
D)  2/ $\pi$ V 
E)  1/50 $\pi$V 
A)  100 V 
B)  200 V 
C)  zero 
D)  2/ $\pi$ V 
E)  1/50 $\pi$V

Question 16

The instantaneous induced EMF in a coil of wire located in a magnetic field

Accepted Answer

A)  depends on the time rate of change of flux through the coil. 
B)  depends on the instantaneous value of flux through the coil. 
C)  is independent of the area of the coil. 
D)  is independent of the number of turns of the coil. 
E)  is determined by the resistance in series with the coil. 
A)  depends on the time rate of change of flux through the coil. 
B)  depends on the instantaneous value of flux through the coil. 
C)  is independent of the area of the coil. 
D)  is independent of the number of turns of the coil. 
E)  is determined by the resistance in series with the coil.

Question 17

A circular loop of radius R has 50 turns. It lies in the xy plane. A time dependent magnetic field   where A is a constant, passes through the loop. The EMF induced in the loop is

Accepted Answer

A)  50 $\pi$AR2 sin ( $ \omega $t) 
B)  50 $\pi$AR2 cos ( $ \omega $t) 
C)  50 $\pi$ $ \omega $AR2 sin ( $ \omega $t) 
D)  50 $\pi$ $ \omega $AR2 cos ( $ \omega $t) 
E)  None of these is correct. 
A)  50 $\pi$AR2 sin ( $ \omega $t) 
B)  50 $\pi$AR2 cos ( $ \omega $t) 
C)  50 $\pi$ $ \omega $AR2 sin ( $ \omega $t) 
D)  50 $\pi$ $ \omega $AR2 cos ( $ \omega $t) 
E)  None of these is correct.

Question 18

According to Faraday's law, a necessary and sufficient condition for an electromotive force to be induced in a closed circuit loop is the presence in the loop of

Accepted Answer

A)  a magnetic field. 
B)  magnetic materials. 
C)  an electric current. 
D)  a time-varying magnetic flux. 
E)  a time-varying magnetic field. 
A)  a magnetic field. 
B)  magnetic materials. 
C)  an electric current. 
D)  a time-varying magnetic flux. 
E)  a time-varying magnetic field.

Question 19

Two identical bar magnets are dropped from equal heights. Magnet A is dropped over bare earth and magnet B over a metal plate. Which magnet strikes first?

Accepted Answer

A)  magnet A 
B)  magnet B 
C)  both strike at the same time 
D)  whichever has its N pole toward the ground 
E)  whichever has its S pole toward the ground 
A)  magnet A 
B)  magnet B 
C)  both strike at the same time 
D)  whichever has its N pole toward the ground 
E)  whichever has its S pole toward the ground

Question 20

In this circuit, $\epsilon$0 = 12 V, R = 6.0 $\Omega$, and L = 0.48 H. The switch is closed at time t = 0. At time t = 0.25 s, the rate of Joule heating is approximately

Accepted Answer

A)  17 W 
B)  22 W 
C)  51 W 
D)  37 W 
E)  11 W 
A)  17 W 
B)  22 W 
C)  51 W 
D)  37 W 
E)  11 W

A device used chiefly for storing energy in a magnetic field is

An LR circuit has a resistance R = 25 $\Omega$ , an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved?

A circular loop of radius 25 cm is sitting in a perpendicular magnetic field of 0.2 T. If the magnetic field strength changes to a value of 0.5 T in 2.5 s, calculate the induced EMF in the loop.

Use the following figure for the next three problems. -A rectangular coil moving at a constant speed v enters a region of uniform magnetic field from the left. While the coil is exiting the field on the right, the direction of the magnetic force is

You place a single loop of wire 0.50 m by 0.30 m perpendicular to a field of 2.0 T. In 30 ms you turn the loop until it is parallel with the field. The average emf induced in this loop is

Which law does the following statement express? "In all cases of electromagnetic induction, the induced voltages have a direction such that the currents they produce oppose the effect that produces them."

A wire rod rolls with a speed of 30 m/s on two metallic rails, 2.0 m apart, that form a closed loop. The power dissipated in the resistor R and the current direction are, respectively,

The magnetic flux through a loop is made to vary according to the relation $\phi$ _m = 6t² + 7t + 1 Where the units are SI. The EMF induced in the loop when t = 2 s is

The plane of a circular, 200-turn coil of radius 5.25 cm is perpendicular to a uniform magnetic field produced by a large electromagnet. This field is changed at a steady rate from 0.650 T to 0.150 T in 0.0100 s. What is the magnitude of the EMF induced in the coil?

How much does the energy stored in an inductor change if the current through the inductor is doubled?

Suppose you double the magnetic field in a given region and quadruple the area through which this magnetic field exists. The effect on the flux through this area would be to

The current in an RL circuit is zero at time t = 0 and increases to 75% of its final value in 4.5 s. The time constant of this circuit is approximately

A region of space contains a magnetic field of 500 G and an electric field of 3 *10⁶ N/C. The total energy density in a cubical box of side = 20 cm in this region is

The magnetic flux through a certain coil is given by $\phi$ _m = (1/50 $\pi$ ) cos 100 $\pi$ t Where the units are SI. The coil has 100 turns. The magnitude of the induced EMF when t = 1/200 s is

The instantaneous induced EMF in a coil of wire located in a magnetic field

A circular loop of radius R has 50 turns. It lies in the xy plane. A time dependent magnetic field where A is a constant, passes through the loop. The EMF induced in the loop is

According to Faraday's law, a necessary and sufficient condition for an electromotive force to be induced in a closed circuit loop is the presence in the loop of

Two identical bar magnets are dropped from equal heights. Magnet A is dropped over bare earth and magnet B over a metal plate. Which magnet strikes first?

The Electric Field I: Discrete Charge Distributions

The Electric Field II: Continuous Charge Distributions

Electric Potential

Capacitance

Electric Current and Direct-Current Circuits

The Magnetic Field

Sources of the Magnetic Field

Alternating-Current Circuits

Maxwells Equations and Electromagnetic Waves

Properties of Light

Optical Images

Interference and Diffraction

Wave Particle Duality and Quantum Physics

Applications of the Schrodinger Equation

Atoms

Molecules

Solids and the Theory of Conduction

Relativity

Nuclear Physics

Elementary Particles and the Beginning of the Universe

Filters

Exam 8: Magnetic Induction

A device used chiefly for storing energy in a magnetic field is

An LR circuit has a resistance R = 25 Ω\OmegaΩ , an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved?

A circular loop of radius 25 cm is sitting in a perpendicular magnetic field of 0.2 T. If the magnetic field strength changes to a value of 0.5 T in 2.5 s, calculate the induced EMF in the loop.

Use the following figure for the next three problems. -A rectangular coil moving at a constant speed v enters a region of uniform magnetic field from the left. While the coil is exiting the field on the right, the direction of the magnetic force is

You place a single loop of wire 0.50 m by 0.30 m perpendicular to a field of 2.0 T. In 30 ms you turn the loop until it is parallel with the field. The average emf induced in this loop is

Which law does the following statement express? "In all cases of electromagnetic induction, the induced voltages have a direction such that the currents they produce oppose the effect that produces them."

A wire rod rolls with a speed of 30 m/s on two metallic rails, 2.0 m apart, that form a closed loop. The power dissipated in the resistor R and the current direction are, respectively,

The magnetic flux through a loop is made to vary according to the relation ϕ\phiϕ m = 6t2 + 7t + 1 Where the units are SI. The EMF induced in the loop when t = 2 s is

The plane of a circular, 200-turn coil of radius 5.25 cm is perpendicular to a uniform magnetic field produced by a large electromagnet. This field is changed at a steady rate from 0.650 T to 0.150 T in 0.0100 s. What is the magnitude of the EMF induced in the coil?

How much does the energy stored in an inductor change if the current through the inductor is doubled?

Suppose you double the magnetic field in a given region and quadruple the area through which this magnetic field exists. The effect on the flux through this area would be to

The current in an RL circuit is zero at time t = 0 and increases to 75% of its final value in 4.5 s. The time constant of this circuit is approximately

A region of space contains a magnetic field of 500 G and an electric field of 3 *106 N/C. The total energy density in a cubical box of side = 20 cm in this region is

The magnetic flux through a certain coil is given by ϕ\phiϕ m = (1/50 π\piπ ) cos 100 π\piπ t Where the units are SI. The coil has 100 turns. The magnitude of the induced EMF when t = 1/200 s is

The instantaneous induced EMF in a coil of wire located in a magnetic field

A circular loop of radius R has 50 turns. It lies in the xy plane. A time dependent magnetic field where A is a constant, passes through the loop. The EMF induced in the loop is

According to Faraday's law, a necessary and sufficient condition for an electromotive force to be induced in a closed circuit loop is the presence in the loop of

Two identical bar magnets are dropped from equal heights. Magnet A is dropped over bare earth and magnet B over a metal plate. Which magnet strikes first?

In this circuit, ϵ\epsilonϵ 0 = 12 V, R = 6.0 Ω\OmegaΩ , and L = 0.48 H. The switch is closed at time t = 0. At time t = 0.25 s, the rate of Joule heating is approximately

The Electric Field I: Discrete Charge Distributions

The Electric Field II: Continuous Charge Distributions

Electric Potential

Capacitance

Electric Current and Direct-Current Circuits

The Magnetic Field

Sources of the Magnetic Field

Alternating-Current Circuits

Maxwells Equations and Electromagnetic Waves

Properties of Light

Optical Images

Interference and Diffraction

Wave Particle Duality and Quantum Physics

Applications of the Schrodinger Equation

Atoms

Molecules

Solids and the Theory of Conduction

Relativity

Nuclear Physics

Elementary Particles and the Beginning of the Universe

Filters

An LR circuit has a resistance R = 25 $\Omega$ , an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved?

The magnetic flux through a loop is made to vary according to the relation $\phi$ _m = 6t² + 7t + 1 Where the units are SI. The EMF induced in the loop when t = 2 s is

A region of space contains a magnetic field of 500 G and an electric field of 3 *10⁶ N/C. The total energy density in a cubical box of side = 20 cm in this region is

The magnetic flux through a certain coil is given by $\phi$ _m = (1/50 $\pi$ ) cos 100 $\pi$ t Where the units are SI. The coil has 100 turns. The magnitude of the induced EMF when t = 1/200 s is