Question 1

A flexible,circular conducting loop of radius 0.15 m and resistance 4.0 -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" > 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.
 -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 WF) A) and B)
G) A) and C)

Question 2

A single conducting loop with an area of 2.0 m² rotates in a uniform magnetic field so that the induced emf has a sinusoidal time dependence as shown.
 
-With what angular frequency does the loop rotate?

Accepted Answer

A)  0.16 rad/s
B)  0.30 rad/s
C)  0.52 rad/s
D)  0.80 rad/s
E)  1.26 rad/sF) A) and D)
G) C) and E)

Question 3

A flexible,circular conducting loop of radius 0.15 m and resistance 4.0 -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" > 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.
 -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 VF) C) and E)
G) All of the above

Question 4

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) A) and C)
G) A) and B)

Question 5

In the drawing,a coil of wire is wrapped around a cylinder from which an iron core extends upward.The ends of the coil are connected to an ac voltage source.After the alternating current is established in the coil,an aluminum ring of resistance R is placed onto the iron core and released.Which one of the following statements concerning this situation is false?

Accepted Answer

A)  The induced current in the ring is an alternating current.
B)  The temperature of the ring will increase.
C)  At any instant,the direction of the induced current in the ring is in the same direction as that in the coil.
D)  The induced magnetic field in the ring may by directed either upward or downward at an instant when the direction of the magnetic field generated by the current in the coil is upward.
E)  The ring may remain suspended at the position shown with no vertical movement of its center of mass.F) A) and C)
G) All of the above

Question 6

A long,straight wire is in the same plane as a rectangular,conducting loop.The wire carries a constant current I as shown in the figure.Which one of the following statements is true if the wire is suddenly moved toward the loop?

Accepted Answer

A)  There will be no induced emf and no induced current.
B)  There will be an induced emf,but no induced current.
C)  There will be an induced current that is clockwise around the loop.
D)  There will be an induced current that is counterclockwise around the loop.
E)  There will be an induced electric field that is clockwise around the loop.F) B) and D)
G) A) and C)

Question 7

A loop with a resistance of 4.0  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 AF) A) and D)
G) B) and D)

Question 8

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.
 
-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.  Which one of the entries in the table below is incorrect?

Accepted Answer

The answer of The figure shows a uniform magnetic field...

Question 9

A loop with a resistance of 4.0  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.
 
-At what rate is energy dissipated by the resistor?

Accepted Answer

A)  130 W
B)  96 W
C)  32 W
D)  49 W
E)  8.0 WF) A) and C)
G) C) and E)

Question 10

A conducting loop has an area of 0.065 m² and is positioned such that a uniform magnetic field is perpendicular to the plane of the loop.When the magnitude of the magnetic field decreases to 0.30 T in 0.087 s,the average induced emf in the loop is 1.2 V.What is the initial value of the magnetic field?

Accepted Answer

A)  0.42 T
B)  0.75 T
C)  0.87 T
D)  1.2 T
E)  1.9 TF) A) and C)
G) All of the above

Question 11

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 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 D)
G) A) and C)

Question 12

A long,straight wire is in the same plane as a wooden,non-conducting loop.The wire carries an increasing current I in the direction shown in the figure.

Accepted Answer

A)  There will be no induced emf and no induced current.
B)  There will be a counterclockwise induced emf,but no induced current.
C)  There will be a clockwise induced emf,but no induced current.
D)  There will be a clockwise induced current in the loop.
E)  There will be a counterclockwise induced current in the loop.F) A) and E)
G) B) and D)

Question 13

A transformer has 450 turns in its primary coil and 30 turns in its secondary coil.Which one of the following statements concerning this transformer is true?

Accepted Answer

A)  This is a step-up transformer.
B)  The turns ratio is 15 for this transformer.
C)  The ratio of the voltages Vs / Vp is 15 for this transformer.
D)  The ratio of the currents Is / Ip is 0.067 for this transformer.
E)  The power delivered to the secondary must be the same as that delivered to the primary.F) A) and B)
G) B) and C)

Question 14

A loop with a resistance of 4.0  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 emf in the loop.

Accepted Answer

A)  2.0 V
B)  4.0 V
C)  8.0 V
D)  14 V
E)  16 VF) A) and E)
G) B) and D)

Question 15

The figure shows a uniform,3.0-T magnetic field that is normal to the plane of a conducting,circular loop with a resistance of 1.5 -³ A,clockwise B) 4.5 × 10-³ A,clockwise C) 4.5 × 10-³ A,counterclockwise D) 9.0 × 10-³ A,clockwise E) 9.0 × 10-³ A,counterclockwise" class="answers-bank-image d-inline" rel="preload" >and a radius of 0.024 m.The magnetic field is directed out of the paper as shown.Note: The area of the non-circular portion of the wire is considered negligible compared to that of the circular loop.
 -³ A,clockwise B) 4.5 × 10-³ A,clockwise C) 4.5 × 10-³ A,counterclockwise D) 9.0 × 10-³ A,clockwise E) 9.0 × 10-³ A,counterclockwise" class="answers-bank-image d-inline" rel="preload" >
-What is the average current around the loop if the magnitude of the magnetic field is doubled in 0.4 s?

Accepted Answer

A)  2.8 × 10-³ A,clockwise
B)  4.5 × 10-³ A,clockwise
C)  4.5 × 10-³ A,counterclockwise
D)  9.0 × 10-³ A,clockwise
E)  9.0 × 10-³ A,counterclockwiseF) None of the above
G) B) and E)

Question 16

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 E)
G) A) and B)

Question 17

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.
 
-Which entry in the table below correctly pairs the change in the system with the direction of the induced current through R?

Accepted Answer

The answer of The figure shows a uniform magnetic field...

Question 18

A 250-turn solenoid carries a current of 9.0 A.The radius of the solenoid is 0.075 m;and its length is 0.14 m.Determine the magnetic flux through the circular cross-sectional area at the center of the solenoid.

Accepted Answer

A)  1.8 × 10-⁵ Wb
B)  9.9 × 10-⁵ Wb
C)  3.6 × 10-⁴ Wb
D)  7.0 × 10-⁴ Wb
E)  2.2 × 10-³ WbF) A) and D)
G) B) and C)

Question 19

A loop with a resistance of 4.0  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.
 
-What is the direction of the magnetic field?

Accepted Answer

A)  to the left
B)  to the right
C)  out of the paper
D)  into the paper
E)  toward the top of the pageF) A) and D)
G) A) and C)

Question 20

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) B) and D)
G) B) and E)

Exam 22: Electromagnetic Induction

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A long,straight wire is in the same plane as a rectangular,conducting loop.The wire carries a constant current I as shown in the figure.Which one of the following statements is true if the wire is suddenly moved toward the loop?

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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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A 250-turn solenoid carries a current of 9.0 A.The radius of the solenoid is 0.075 m;and its length is 0.14 m.Determine the magnetic flux through the circular cross-sectional area at the center of the solenoid.

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A long,straight wire is in the same plane as a wooden,non-conducting loop.The wire carries an increasing current I in the direction shown in the figure.

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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?

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A transformer has 450 turns in its primary coil and 30 turns in its secondary coil.Which one of the following statements concerning this transformer is true?

Correct Answer
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A single conducting loop with an area of 2.0 m² rotates in a uniform magnetic field so that the induced emf has a sinusoidal time dependence as shown. -With what angular frequency does the loop rotate?

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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?

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Exam 22: Electromagnetic Induction

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A long,straight wire is in the same plane as a rectangular,conducting loop.The wire carries a constant current I as shown in the figure.Which one of the following statements is true if the wire is suddenly moved toward the loop?

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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?

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A 250-turn solenoid carries a current of 9.0 A.The radius of the solenoid is 0.075 m;and its length is 0.14 m.Determine the magnetic flux through the circular cross-sectional area at the center of the solenoid.

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A long,straight wire is in the same plane as a wooden,non-conducting loop.The wire carries an increasing current I in the direction shown in the figure.

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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?

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Correct AnswerverifiedShow Answer

A transformer has 450 turns in its primary coil and 30 turns in its secondary coil.Which one of the following statements concerning this transformer is true?

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A single conducting loop with an area of 2.0 m² rotates in a uniform magnetic field so that the induced emf has a sinusoidal time dependence as shown. -With what angular frequency does the loop rotate?

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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?

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