Question 1

Two conducting loops carry equal currents I in the same direction as shown in the figure. If the current in the upper loop suddenly drops to zero, what will happen to the current in the lower loop according to Lenz's law?

Accepted Answer

A)  The current in the lower loop will decrease.
B)  The current in the lower loop will increase.
C)  The current in the lower loop will not change.
D)  The current in the lower loop will also drop to zero.
E)  The current in the lower loop will reverse its direction.F) C) and D)
G) B) and D)

Question 2

A 0.100-m long solenoid has a radius of 0.050 m and 1.50 × 104 turns. The current in the solenoid changes at a rate of 6.0 A/s. A conducting loop of radius 0.0200 m is placed at the center of the solenoid with its axis the same as that of the solenoid as shown. 4 turns. The current in the solenoid changes at a rate of 6.0 A/s. A conducting loop of radius 0.0200 m is placed at the center of the solenoid with its axis the same as that of the solenoid as shown.   -Determine the mutual inductance of this combination. A) 1.8 × 10-4 H B) 2.4 × 10-4 H C) 3.6 × 10-4 H D) 4.4 × 10-4 H E) 5.9 × 10-4 H" class="answers-bank-image d-inline" rel="preload" >
-Determine the mutual inductance of this combination.

Accepted Answer

A)  1.8 × 10-4 H
B)  2.4 × 10-4 H
C)  3.6 × 10-4 H
D)  4.4 × 10-4 H
E)  5.9 × 10-4 HF) B) and D)
G) None of the above

Question 3

Which one of the following statements concerning transformers is false?

Accepted Answer

A)  Their operation makes use of mutual induction.
B)  They are an application of Faraday's and Lenz's laws.
C)  A transformer can function with either an ac current or a steady dc current.
D)  A transformer that steps down the voltage, steps up the current.
E)  A transformer that steps up the voltage, steps down the current.F) B) and D)
G) None of the above

Question 4

A flexible, circular conducting loop of radius 0.15 m and resistance 4.0  Ω\varOmegaΩ  lies in a uniform magnetic field of 0.25 T. The loop is pulled on opposite sides by equal forces and stretched until its enclosed area is essentially zero m2, as suggested in the drawings. It takes 0.30 s to close the loop. 2, as suggested in the drawings. It takes 0.30 s to close the loop.   -At what rate is heat generated in the loop? A) 3.6 × 10-3 W B) 8.7 × 10-4 W C) 8.7 × 104 W D) 8.1 × 105 W E) 8.1 × 10-5 W " class="answers-bank-image d-inline" rel="preload" >
-At what rate is heat generated in the loop?

Accepted Answer

A)  3.6 × 10-3 W
B)  8.7 × 10-4 W
C)  8.7 × 104 W
D)  8.1 × 105 W
E)  8.1 × 10-5 W F) A) and E)
G) A) and D)

Question 5

A circular coil of wire has 25 turns and has a radius of 0.075 m. The coil is located in a variable magnetic field whose behavior is shown on the graph. At all times, the magnetic field is directed at an angle of 75° relative to the normal to the plane of a loop. What is the average emf induced in the coil in the time interval from t = 5.00 s to 7.50 s?

Accepted Answer

A)  -18 mV
B)  -49 mV
C)  -92 mV
D)  -140 mV
E)  -180 mVF) B) and C)
G) A) and E)

Question 6

The angular speed of a motor is 262 rad/s. The back emf generated by the motor is 89.4 V. Assuming all other factors remain the same, determine the back emf if the angular speed of the motor is reduced to 131 rad/s.

Accepted Answer

A)  32.3 V
B)  44.7 V
C)  52.5 V
D)  89.4 V
E)  152 VF) C) and D)
G) A) and B)

Question 7

A flexible, circular conducting loop of radius 0.15 m and resistance 4.0  Ω\varOmegaΩ  lies in a uniform magnetic field of 0.25 T. The loop is pulled on opposite sides by equal forces and stretched until its enclosed area is essentially zero m2, as suggested in the drawings. It takes 0.30 s to close the loop. 2, as suggested in the drawings. It takes 0.30 s to close the loop.   -Determine the magnitude of the emf induced in the loop. A) 1.2 × 10-1 V B) 1.8 × 10-2 V C) 1.8 × 102 V D) 5.9 × 10-2 V E) 5.9 × 102 V " class="answers-bank-image d-inline" rel="preload" >
-Determine the magnitude of the emf induced in the loop.

Accepted Answer

A)  1.2 × 10-1 V
B)  1.8 × 10-2 V
C)  1.8 × 102 V
D)  5.9 × 10-2 V
E)  5.9 × 102 V F) All of the above
G) B) and E)

Question 8

A 0.100-m long solenoid has a radius of 0.050 m and 1.50 × 104 turns. The current in the solenoid changes at a rate of 6.0 A/s. A conducting loop of radius 0.0200 m is placed at the center of the solenoid with its axis the same as that of the solenoid as shown. 4 turns. The current in the solenoid changes at a rate of 6.0 A/s. A conducting loop of radius 0.0200 m is placed at the center of the solenoid with its axis the same as that of the solenoid as shown.   -Determine the induced emf in the loop if the loop is oriented so that its axis is perpendicular to the axis of the solenoid, instead of parallel. A) 0.7 × 10-4 V B) 1.4 × 10-4 V C) 2.8 × 10-4 V D) 5.6 × 10-4 V E) zero volts" class="answers-bank-image d-inline" rel="preload" >
-Determine the induced emf in the loop if the loop is oriented so that its axis is perpendicular to the axis of the solenoid, instead of parallel.

Accepted Answer

A)  0.7 × 10-4 V
B)  1.4 × 10-4 V
C)  2.8 × 10-4 V
D)  5.6 × 10-4 V
E)  zero voltsF) A) and B)
G) A) and C)

Question 9

A small power plant produces a voltage of 6.0 kV and 150 A. The voltage is stepped up to 240 kV by a transformer before it is transmitted to a substation. The resistance of the transmission line between the power plant and the substation is 75  Ω\varOmegaΩ .
-What percentage of the power produced at the power plant is lost in transmission to the substation?

Accepted Answer

A)  0.47 %
B)  0.41 %
C)  0.34 %
D)  0.23 %
E)  0.12 % F) C) and D)
G) A) and C)

Question 10

A solenoid with 1000 turns has a cross-sectional area of 7.0 cm2 and length of 25 cm. How much energy is stored in the magnetic field of the solenoid when it carries a current of 10.0 A?

Accepted Answer

A)  0.10 J
B)  2.8 J
C)  0.18 J
D)  28 J
E)  0.36 JF) A) and B)
G) B) and E)

Question 11

The Earth's magnetic field passes through a square tabletop with a magnitude of 4.95 × 10-5 T and is directed at an angle of 165° relative to the normal of the tabletop. If the tabletop has 1.50-m sides, what is the magnitude of the magnetic flux through it?

Accepted Answer

A)  1.08 × 10-4 Wb
B)  7.11 × 10-5 Wb
C)  2.88 × 10-5 Wb
D)  1.92 × 10-5 Wb
E)  3.30 × 10-6 WbF) A) and D)
G) B) and E)

Question 12

A loop with a resistance of 4.0  Ω\varOmegaΩ  is pushed to the left at a constant speed of 2.0 m/s by a 24 N force. At the instant shown in the figure, the loop is partially in and partially out of a uniform magnetic field. An induced current flows from left to right through the resistor. The length and width of the loop are 2.0 m and 1.0 m, respectively. 
-Determine the magnitude of the uniform magnetic field.

Accepted Answer

A)  2.2 T
B)  3.5 T
C)  6.4 T
D)  7.0 T
E)  9.1 T F) A) and E)
G) None of the above

Question 13

A transformer changes 120 V across the primary to 1200 V across the secondary. If the secondary coil has 800 turns, how many turns does the primary coil have?

Accepted Answer

A)  40
B)  80
C)  100
D)  400
E)  4000F) A) and D)
G) B) and D)

Question 14

The figure shows a uniform magnetic field that is normal to the plane of the conducting loop of resistance R. Note: the area of the non-circular portion of the circuit is negligible compared to that of the loop. 2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   A)    B)    C)    D)    E)   " class="answers-bank-image d-inline" rel="preload" >
-A circular loop of copper wire with an area of 2.0 m2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph. 2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   A)    B)    C)    D)    E)   " class="answers-bank-image d-inline" rel="preload" > Which one of the entries in the table below is incorrect? 2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   A)    B)    C)    D)    E)   " class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
B)   2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
C)   2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
D)   2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >
E)   2 lies in a plane perpendicular to a time-dependent magnetic field oriented as shown. The time-dependence of the field is shown in the graph.   Which one of the entries in the table below is incorrect?   
A)     
B)     
C)     
D)     
E)    " class="answers-bank-image d-inline" rel="preload" >F) A) and E)
G) C) and E)

Question 15

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. 
-Assume S has been closed for a long time. Which one of the following statements is true when coil 1 and its core are moved toward point B?

Accepted Answer

A)  There is no induced current in r.
B)  There is a magnetic field in coil 1 that points toward B.
C)  There is an induced current in R that flows from left to right.
D)  There is an induced current in R that flows from right to left.
E)  There is an induced magnetic field in coil 2 that points toward B.F) None of the above
G) A) and C)

Question 16

A loop with a resistance of 4.0  Ω\varOmegaΩ  is pushed to the left at a constant speed of 2.0 m/s by a 24 N force. At the instant shown in the figure, the loop is partially in and partially out of a uniform magnetic field. An induced current flows from left to right through the resistor. The length and width of the loop are 2.0 m and 1.0 m, respectively. 
-Determine the magnitude of the induced current through the resistor.

Accepted Answer

A)  2.0 A
B)  3.5 A
C)  4.6 A
D)  7.2 A
E)  11 A F) D) and E)
G) A) and D)

Question 17

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. 
-Assume that S has been closed for a long time. Which one of the following changes will result in an induced magnetic field in coil 2 that points toward C?

Accepted Answer

A)  The switch S is opened.
B)  The iron core is removed from coil 1.
C)  Coil 1 and its core are moved toward A.
D)  Coil 1 and its core are moved toward B.
E)  Coil 2 and its core are moved toward C.F) B) and C)
G) A) and E)

Question 18

The figure shows a uniform magnetic field that is normal to the plane of a conducting loop with resistance R. Which one of the following changes will cause an induced current to flow through the resistor?

Accepted Answer

A)  decreasing the area of the loop
B)  decreasing the magnitude of the magnetic field
C)  increasing the magnitude of the magnetic field
D)  rotating the loop through 90° about an axis in the plane of the paper
E)  all of the aboveF) A) and C)
G) C) and E)

Question 19

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. 
-Assume that S has been closed for a long time. Which one of the following statements is true if S is suddenly opened?

Accepted Answer

A)  There is no induced current through R.
B)  There is no induced magnetic field in coil 2.
C)  There is an induced current in R that flows from right to left.
D)  There is an induced magnetic field in coil 2 that points toward C.
E)  There is an induced magnetic field in coil 2 that points toward B.F) B) and D)
G) A) and E)

Question 20

A 1.2-kg rod that has a length of 1.0 m and a resistance of 5.0  Ω\varOmegaΩ  slides with constant speed down a pair of frictionless vertical conducting rails that are joined at the bottom. Other than the rod, the rest of the circuit is resistanceless. A uniform magnetic field of magnitude 3.0 T is perpendicular to the plane formed by the rod and the rails as shown. Determine the speed of the rod.

Accepted Answer

A)  0.38 m/s
B)  0.90 m/s
C)  2.6 m/s
D)  6.5 m/s
E)  8.7 m/s F) All of the above
G) A) and B)

Exam 22: Electromagnetic Induction

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume S has been closed for a long time. Which one of the following statements is true when coil 1 and its core are moved toward point B?

Correct Answer
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Which one of the following statements concerning transformers is false?

Correct Answer
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Correct Answer
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Correct Answer
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Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume that S has been closed for a long time. Which one of the following changes will result in an induced magnetic field in coil 2 that points toward C?

Correct Answer
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Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume that S has been closed for a long time. Which one of the following statements is true if S is suddenly opened?

Correct Answer
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A solenoid with 1000 turns has a cross-sectional area of 7.0 cm² and length of 25 cm. How much energy is stored in the magnetic field of the solenoid when it carries a current of 10.0 A?

Correct Answer
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Correct Answer
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Correct Answer
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The Earth's magnetic field passes through a square tabletop with a magnitude of 4.95 × 10^-⁵ T and is directed at an angle of 165° relative to the normal of the tabletop. If the tabletop has 1.50-m sides, what is the magnitude of the magnetic flux through it?

Correct Answer
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A transformer changes 120 V across the primary to 1200 V across the secondary. If the secondary coil has 800 turns, how many turns does the primary coil have?

Correct Answer
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Correct Answer
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The angular speed of a motor is 262 rad/s. The back emf generated by the motor is 89.4 V. Assuming all other factors remain the same, determine the back emf if the angular speed of the motor is reduced to 131 rad/s.

Correct Answer
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Correct Answer
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Two conducting loops carry equal currents I in the same direction as shown in the figure. If the current in the upper loop suddenly drops to zero, what will happen to the current in the lower loop according to Lenz's law?

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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The figure shows a uniform magnetic field that is normal to the plane of a conducting loop with resistance R. Which one of the following changes will cause an induced current to flow through the resistor?

Correct Answer
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Exam 22: Electromagnetic Induction

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume S has been closed for a long time. Which one of the following statements is true when coil 1 and its core are moved toward point B?

Correct AnswerverifiedShow Answer

Which one of the following statements concerning transformers is false?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume that S has been closed for a long time. Which one of the following changes will result in an induced magnetic field in coil 2 that points toward C?

Correct AnswerverifiedShow Answer

Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. -Assume that S has been closed for a long time. Which one of the following statements is true if S is suddenly opened?

Correct AnswerverifiedShow Answer

A solenoid with 1000 turns has a cross-sectional area of 7.0 cm2 and length of 25 cm. How much energy is stored in the magnetic field of the solenoid when it carries a current of 10.0 A?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The Earth's magnetic field passes through a square tabletop with a magnitude of 4.95 × 10-5 T and is directed at an angle of 165° relative to the normal of the tabletop. If the tabletop has 1.50-m sides, what is the magnitude of the magnetic flux through it?

Correct AnswerverifiedShow Answer

A transformer changes 120 V across the primary to 1200 V across the secondary. If the secondary coil has 800 turns, how many turns does the primary coil have?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The angular speed of a motor is 262 rad/s. The back emf generated by the motor is 89.4 V. Assuming all other factors remain the same, determine the back emf if the angular speed of the motor is reduced to 131 rad/s.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Two conducting loops carry equal currents I in the same direction as shown in the figure. If the current in the upper loop suddenly drops to zero, what will happen to the current in the lower loop according to Lenz's law?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The figure shows a uniform magnetic field that is normal to the plane of a conducting loop with resistance R. Which one of the following changes will cause an induced current to flow through the resistor?

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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A solenoid with 1000 turns has a cross-sectional area of 7.0 cm² and length of 25 cm. How much energy is stored in the magnetic field of the solenoid when it carries a current of 10.0 A?

Correct Answer
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Correct Answer
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Correct Answer
verified

The Earth's magnetic field passes through a square tabletop with a magnitude of 4.95 × 10^-⁵ T and is directed at an angle of 165° relative to the normal of the tabletop. If the tabletop has 1.50-m sides, what is the magnitude of the magnetic flux through it?

Correct Answer
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Correct Answer
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