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Deck 23: Magnetic Flux and Faradays Law of Induction
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Question
A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is pulled upward,what is the direction of the current induced in the ring,as viewed from above? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
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A bar magnet is oriented above a copper ring,as shown in the figure.The magnet is dropped and passes completely through the ring.As viewed from above,what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
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A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is kept fixed while the ring is dropped,what is the direction of the current induced in the ring,as viewed from below the ring? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
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The three loops of wire shown in the figure are all hanging in the same uniform magnetic field 
That is perpendicular to the page and does not vary with time.Loop 1 swings back and forth like the bob in a pendulum,Loop 2 rotates about a vertical axis,and Loop 3 oscillates up and down at the end of a spring.Which loop (or loops)will have an emf induced in them?
A)Loop 1
B)Loop 2
C)Loop 3
D)Loops 1 and 3
E)Loops 2 and 3
That is perpendicular to the page and does not vary with time.Loop 1 swings back and forth like the bob in a pendulum,Loop 2 rotates about a vertical axis,and Loop 3 oscillates up and down at the end of a spring.Which loop (or loops)will have an emf induced in them?
A)Loop 1
B)Loop 2
C)Loop 3
D)Loops 1 and 3
E)Loops 2 and 3
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An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring? 
A)clockwise
B)counterclockwise
C)There is no induced current in the inner ring.
A)clockwise
B)counterclockwise
C)There is no induced current in the inner ring.
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Two solenoids are close to each other,as shown in the figure,with the switch S open.When the switch is suddenly closed,which way will the induced current flow through the galvanometer in the left-hand solenoid? 
A)from left to right
B)from right to left
C)There will be no induced current through the galvanometer.
A)from left to right
B)from right to left
C)There will be no induced current through the galvanometer.
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As shown in the figure,a battery supplies a steady current to the solenoid on the left.The two solenoids are moving toward each other with speeds v.The direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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As shown in the figure,a straight wire carries a current I into the page.The wire passes through the center of a toroidal coil.If the current I is quickly reduced to zero,the direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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As shown in the figure,two parallel wires carry a current I in opposite directions,and this current is decreasing.A rectangular loop is centered between the wires.The direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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A circular wire ring is situated above a long straight wire,as shown in the figure.The straight wire has a current I flowing to the right,and this current is increasing at a constant rate.Which of the following statements is true? 
A)There is an induced current in the wire ring,directed in clockwise orientation.
B)There is an induced current in the wire ring,directed in a counterclockwise orientation.
C)There is no induced current in the wire ring.
A)There is an induced current in the wire ring,directed in clockwise orientation.
B)There is an induced current in the wire ring,directed in a counterclockwise orientation.
C)There is no induced current in the wire ring.
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As shown in the figure,a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν.A uniform magnetic field is present,directed downward as shown.The direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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As shown in the figure,two solenoids are side by side.The switch S is initially open.When S is suddenly closed,the direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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As shown in the figure,one end of a metal bar is in contact with a circular rail and the other end is pivoted at P.A steady uniform,magnetic field B into the page is present.As the bar rotates about point P in a clockwise direction,the direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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As shown in the figure,a C-shaped conductor is in a uniform magnetic field B out of the page,and this field is increasing.What is the polarity of the induced emf in terminals X and Y? 
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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As shown in the figure,a metal bar is in contact with a pair of metal parallel rails.A steady uniform magnetic field B,perpendicular to the plane of the rails and pointing outward from the page,is present.The bar is in downward motion with velocity of magnitude ν.The direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
Question
As shown in the figure,two solenoids are in line.The switch S,initially closed,is suddenly opened.Just after opening S,what is the polarity of the induced emf in terminals X and Y? 
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
Question
The wire in the figure carries a current I that is increasing with time at a constant rate.The wire and the three loops are all in the same plane.What is true about the currents induced in each of the three loops shown? 
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
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The wire in the figure carries a current I that is decreasing with time at a constant rate.The wire and the three loops are all in the same plane.What is true about the currents induced in each of the three loops shown? 
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
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As shown in the figure,a metal bar is in contact with a pair of parallel rails.A steady,uniform,magnetic field B is present directed to the right.The bar is moving upward with velocity of magnitude ν.What is the polarity of the induced emf in terminals X and Y? 
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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In the figure,a bar magnet moves away from the solenoid.The direction of the induced current through the resistor R is 
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
Question
The wire in the figure carries a steady current I.What is true about the currents induced in each of the three loops shown? The wire and the three loops are all in the same plane. 
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
Question
As shown in the figure,a coil of wire is placed in the xy-plane,centered on the z-axis.A solenoid is centered on the z-axis and is carrying a steady dc current.Which one of the following actions will not result induce an emf in the coil? 
A)Rotate the coil about the x-axis.
B)Rotate the coil about the y-axis.
C)Rotate the coil about the z-axis.
D)Move the coil toward point P.
E)Change the current in the solenoid.
A)Rotate the coil about the x-axis.
B)Rotate the coil about the y-axis.
C)Rotate the coil about the z-axis.
D)Move the coil toward point P.
E)Change the current in the solenoid.
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As shown in the figure,a straight wire carries a steady current I.A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude ν.The polarity of the induced emf in terminals X and Y is 
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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A conductor is formed into a flat loop that encloses an area of 
The plane of the loop is oriented at a 30.0° angle with the xy-plane.A uniform time-varying magnetic field is oriented parallel to the z-axis.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing?
A)29 T/s
B)22 T/s
C)50 T/s
D)13 T/s
The plane of the loop is oriented at a 30.0° angle with the xy-plane.A uniform time-varying magnetic field is oriented parallel to the z-axis.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing?
A)29 T/s
B)22 T/s
C)50 T/s
D)13 T/s
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A bar magnet is pushed through a coil of wire of cross-sectional area 0.020 m2 as shown in the figure.The coil has seven turns,and the rate of change of the strength of the magnetic field in it due to the motion of the bar magnet is 0.040 T/s.What is the magnitude of the induced emf in that coil of wire? 
A)5.6 × 10-3 V
B)5.6 × 10-2 V
C)5.6 × 10-1 V
D)5.6 × 10-4 V
E)5.6 × 10-5 V
A)5.6 × 10-3 V
B)5.6 × 10-2 V
C)5.6 × 10-1 V
D)5.6 × 10-4 V
E)5.6 × 10-5 V
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A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field? 
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
Question
A circular coil of 20 turns and radius 5.0 cm is placed with its plane oriented at 90° to a uniform magnetic field of 
The field is now increased at a steady rate,reaching a value of
After 4.0 seconds.What emf is induced in the coil?
A)0.016 V
B)0.021 V
C)0.026 V
D)0.031 V
E)0.036 V
The field is now increased at a steady rate,reaching a value of
After 4.0 seconds.What emf is induced in the coil?
A)0.016 V
B)0.021 V
C)0.026 V
D)0.031 V
E)0.036 V
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A closed flat loop conductor with radius 
Is located in a changing uniform magnetic field.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?
A)0.16 T/s
B)1.0 T/s
C)0.080 T/s
D)2.0 T/s
Is located in a changing uniform magnetic field.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?
A)0.16 T/s
B)1.0 T/s
C)0.080 T/s
D)2.0 T/s
Question
A circular conducting loop with a radius of 
And a small gap filled with a
Resistor is oriented in the
If a uniform magnetic field of
Making an angle of
With the
Increases to
In
What is the magnitude of the current that will be caused to flow in the loop if it has negligible resistance?
A)0.01530393 A
B)0.08835729 A
C)0.15303932 A
D)0 A
And a small gap filled with a
Resistor is oriented in the
If a uniform magnetic field of
Making an angle of
With the
Increases to
In
What is the magnitude of the current that will be caused to flow in the loop if it has negligible resistance?
A)0.01530393 A
B)0.08835729 A
C)0.15303932 A
D)0 A
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A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop makes an angle of 60° with the magnetic field? 
A)2.6 × 10-3 T ∙ m2
B)1.3 × 10-3 T ∙ m2
C)0 T ∙ m2
D)2.2 × 10-3 T ∙ m2
E)0.80 T ∙ m2
A)2.6 × 10-3 T ∙ m2
B)1.3 × 10-3 T ∙ m2
C)0 T ∙ m2
D)2.2 × 10-3 T ∙ m2
E)0.80 T ∙ m2
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A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop is perpendicular to the magnetic field? 
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
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A conducting rod whose length is ℓ = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper.What is the magnitude of the external applied force needed to move the rod to the right with a constant speed of 6.00 m/s? 
A)8.60 N
B)9.30 N
C)10.6 N
D)12.6 N
E)18.6 N
A)8.60 N
B)9.30 N
C)10.6 N
D)12.6 N
E)18.6 N
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It is known that birds can detect the earth's magnetic field,but the mechanism of how they do this is not known.It has been suggested that perhaps they detect a motional emf as they fly north to south,but it turns out that the induced voltages are small compared to the voltages normally encountered in cells,so this is probably not the mechanism involved.To check this out,calculate the induced voltage across the wingtips of a wild goose with a wingspan of 
If it is flying directly south at
At a point where the earth's magnetic field is 5.0 × 10-5 T directed downward from the horizontal by
A)0.50 mV
B)0.60 mV
C)0.78 mV
D)0.060 mV
E)0.25 mV
If it is flying directly south at
At a point where the earth's magnetic field is 5.0 × 10-5 T directed downward from the horizontal by
A)0.50 mV
B)0.60 mV
C)0.78 mV
D)0.060 mV
E)0.25 mV
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A conducting rod whose length is ℓ = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the right with a constant speed of 6.00 m/s.At what rate is energy dissipated in the lightbulb? 
A)60.0 W
B)121 W
C)21.2 W
D)112 W
E)11.5 W
A)60.0 W
B)121 W
C)21.2 W
D)112 W
E)11.5 W
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A round flat metal coil has 180 turns and negligible resistance.It is connected in a series circuit with a 
Resistor,with nothing else in the circuit.You measure that a
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at
What is the radius of the coil?
A)0.25 m
B)0.014 m
C)0.54 m
D)0.043 m
Resistor,with nothing else in the circuit.You measure that a
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at
What is the radius of the coil?
A)0.25 m
B)0.014 m
C)0.54 m
D)0.043 m
Question
A round flat conducting loop is placed perpendicular to a uniform 0.50 T magnetic field.If the area of the loop increases at a rate of 3.0 × 
/s,what is the induced emf in the loop?
A)4.3 mV
B)0 mV
C)1.5 mV
D)1.7 mV
E)5.5 mV
/s,what is the induced emf in the loop?
A)4.3 mV
B)0 mV
C)1.5 mV
D)1.7 mV
E)5.5 mV
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A long vertical wire carries a steady 70 A current.As shown in the figure,a pair of horizontal rails are 0.20 m apart.A 20-Ω resistor connects points a and b,at the end of the rails.A bar is in contact with the rails,and is moved by an external force with a constant horizontal velocity of 0.90 m/s to the right,as shown.The bar and the rails have negligible resistance.At the instant that the bar is 0.20 m from the wire,what are the induced current in the resistor and its direction through the resistor? (μ0 = 4π × 10-7 T ∙ m/A) 
A)0.63 μA,from a to b
B)0.63 μA,from b to a
C)0.32 μA,from a to b
D)0.32 μA,from b to a
E)1.9 μA,from b to a
A)0.63 μA,from a to b
B)0.63 μA,from b to a
C)0.32 μA,from a to b
D)0.32 μA,from b to a
E)1.9 μA,from b to a
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An electromagnetic flowmeter is useful when it is desirable not to interrupt the system in which the fluid is flowing (such as the blood in an artery during heart surgery).Such a device is illustrated in the figure.The conducting fluid moves with speed v in a tube of diameter d.Perpendicular to this tube is a magnetic field B.A voltage V is induced between opposite sides of the tube due to the motion of the conducting fluid in the magnetic field.For a certain case,B = 0.120 T,d = 1.2 cm,and the measured voltage is 
Determine the speed of the fluid.
A)2.0 m/s
B)11 m/s
C)0.075 m/s
D)1.1 m/s
E)750 m/s
Determine the speed of the fluid.
A)2.0 m/s
B)11 m/s
C)0.075 m/s
D)1.1 m/s
E)750 m/s
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A conducting rod whose length is ℓ = 27.0 cm is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 5.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 1.20 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the right with a constant speed.At what speed should the rod be pulled so that the lightbulb will consume energy at a rate of 1.10 W? 
A)2.00 m/s
B)3.50 m/s
C)4.26 m/s
D)6.00 m/s
E)7.24 m/s
A)2.00 m/s
B)3.50 m/s
C)4.26 m/s
D)6.00 m/s
E)7.24 m/s
Question
A conducting rod with a length ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and into the paper.An external applied force moves the rod to the right with a constant speed of 6.0 m/s.What are the magnitude and direction of the induced current in the circuit? 
A)17 mA clockwise
B)17 mA counterclockwise
C)75 mA counterclockwise
D)75 mA clockwise
E)52 mA clockwise
A)17 mA clockwise
B)17 mA counterclockwise
C)75 mA counterclockwise
D)75 mA clockwise
E)52 mA clockwise
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The area of a rectangular loop of wire is 3.6 × 
.The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?
A)2.8 ×
V
B)2.7 ×
V
C)0 V
D)1.8 ×
V
E)3.0 ×
V
.The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?
A)2.8 ×
VB)2.7 ×
VC)0 V
D)1.8 ×
VE)3.0 ×
V Question
As shown in the figure,a wire and a 10-Ω resistor are used to form a circuit in the shape of a square with dimensions 20 cm by 20 cm.A uniform but non-steady magnetic field is directed into the plane of the circuit.The magnitude of the magnetic field is steadily decreased from 2.70 T to 0.90 T in a time interval of 96 ms.What is the induced current in the circuit,and what is its direction through the resistor? 
A)75 mA,from b to a
B)45 mA,from b to a
C)75 mA,from a to b
D)45 mA,from a to b
E)110 mA,from a to b
A)75 mA,from b to a
B)45 mA,from b to a
C)75 mA,from a to b
D)45 mA,from a to b
E)110 mA,from a to b
Question
A conducting rod of length ℓ= 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω,as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and into the paper.An applied external force pulls the rod to the right with a constant speed of 6.0 m/s.What is the magnitude of the emf induced in the rod? 
A)0.20 V
B)0.30 V
C)0.40 V
D)0.50 V
E)0.60 V
A)0.20 V
B)0.30 V
C)0.40 V
D)0.50 V
E)0.60 V
Question
A constant uniform magnetic field of 0.50 T is applied at right angles to the plane of a flat rectangular loop of area 3.0 × 
.If the area of this loop changes steadily from its original value to a new value of 1.6 × 10-3 m2 in 1.6 s,what is the emf induced in the loop?
A)1.6 ×
V
B)0 V
C)7.5 ×
V
D)4.4 ×
V
E)9.0 ×
V
.If the area of this loop changes steadily from its original value to a new value of 1.6 × 10-3 m2 in 1.6 s,what is the emf induced in the loop?
A)1.6 ×
VB)0 V
C)7.5 ×
VD)4.4 ×
VE)9.0 ×
V Question
A conducting rod whose length is ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the left with a constant speed of 12 m/s.What are the magnitude and direction of the induced current in the circuit? 
A)150 mA clockwise
B)150 mA counterclockwise
C)34 mA counterclockwise
D)34 mA clockwise
E)100 mA clockwise
A)150 mA clockwise
B)150 mA counterclockwise
C)34 mA counterclockwise
D)34 mA clockwise
E)100 mA clockwise
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Deck 23: Magnetic Flux and Faradays Law of Induction
1
A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is pulled upward,what is the direction of the current induced in the ring,as viewed from above?
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
counterclockwise
2
A circular coil of copper wire is lying flat on a horizontal table.A bar magnet is held above the center of the coil with its south pole downward.The magnet and the coil are now both raised upward with the same velocities.As viewed from above,what is the direction of the current induced in the coil as the magnet approaches the coil?
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.
No current is induced in the coil.
3
A bar magnet is oriented above a copper ring,as shown in the figure.The magnet is dropped and passes completely through the ring.As viewed from above,what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
counterclockwise
4
A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up.The magnetic field suddenly grows stronger.When viewed from above,what is the direction of the induced current in this coil as the field increases?
A)counterclockwise
B)clockwise
C)clockwise initially,then counterclockwise before stopping
D)There is no induced current in this coil.
A)counterclockwise
B)clockwise
C)clockwise initially,then counterclockwise before stopping
D)There is no induced current in this coil.
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5
At a certain instant,coil A is in a 10-T external magnetic field and coil B is in a 1-T external magnetic field.Both coils have the same area and are oriented at right angles to the field.Which coil will have a greater emf induced in it?
A)coil A
B)coil B
C)It is impossible to know without more information about the fields.
A)coil A
B)coil B
C)It is impossible to know without more information about the fields.
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6
According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic flux through the circuit.
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7
A circular coil lies flat on a horizontal surface.A bar magnet is held fixed above the center of the coil with its north pole pointing downward.What is the direction of the induced current in the coil,as viewed from above?
A)clockwise
B)counterclockwise
C)There is no current in the coil.
A)clockwise
B)counterclockwise
C)There is no current in the coil.
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8
A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is kept fixed while the ring is dropped,what is the direction of the current induced in the ring,as viewed from below the ring?
A)There is no current in the ring.
B)counterclockwise
C)clockwise
A)There is no current in the ring.
B)counterclockwise
C)clockwise
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9
The three loops of wire shown in the figure are all hanging in the same uniform magnetic field
That is perpendicular to the page and does not vary with time.Loop 1 swings back and forth like the bob in a pendulum,Loop 2 rotates about a vertical axis,and Loop 3 oscillates up and down at the end of a spring.Which loop (or loops)will have an emf induced in them?
A)Loop 1
B)Loop 2
C)Loop 3
D)Loops 1 and 3
E)Loops 2 and 3
That is perpendicular to the page and does not vary with time.Loop 1 swings back and forth like the bob in a pendulum,Loop 2 rotates about a vertical axis,and Loop 3 oscillates up and down at the end of a spring.Which loop (or loops)will have an emf induced in them?
A)Loop 1
B)Loop 2
C)Loop 3
D)Loops 1 and 3
E)Loops 2 and 3
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10
A coil lies flat on a tabletop in a region where the magnetic field vector points straight up.The magnetic field vanishes suddenly.When viewed from above,what is the sense of the induced current in this coil as the field fades?
A)The induced current flows counterclockwise.
B)The induced current flows clockwise.
C)There is no induced current in this coil.
D)The current flows clockwise initially,and then it flows counterclockwise before stopping.
A)The induced current flows counterclockwise.
B)The induced current flows clockwise.
C)There is no induced current in this coil.
D)The current flows clockwise initially,and then it flows counterclockwise before stopping.
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11
According to Faraday's law,a coil in a strong magnetic field must have a greater induced emf in it than a coil in a weak magnetic field.
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12
According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic field through the circuit.
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13
A circular coil of copper wire is lying flat on a horizontal table.A bar magnet is held above the center of the coil with its south pole downward.The magnet is released from rest and falls toward the coil.As viewed from above,what is the direction of the current induced in the coil as the magnet approaches the coil?
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.
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14
An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring?
A)clockwise
B)counterclockwise
C)There is no induced current in the inner ring.
A)clockwise
B)counterclockwise
C)There is no induced current in the inner ring.
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15
Two solenoids are close to each other,as shown in the figure,with the switch S open.When the switch is suddenly closed,which way will the induced current flow through the galvanometer in the left-hand solenoid?
A)from left to right
B)from right to left
C)There will be no induced current through the galvanometer.
A)from left to right
B)from right to left
C)There will be no induced current through the galvanometer.
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16
A circular coil lies flat on a horizontal surface.A bar magnet is held above the center of the coil with its north pole pointing down.If the magnet is dropped from this position what is the direction of the induced current in the coil,as viewed from above?
A)counterclockwise
B)clockwise
C)An emf but no current is induced in the coil.
D)There is no current in the coil.
A)counterclockwise
B)clockwise
C)An emf but no current is induced in the coil.
D)There is no current in the coil.
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17
A long straight wire lies on a horizontal table and carries an ever-increasing current toward the north.Two coils of wire lie flat on the table,one on either side of the wire.When viewed from above,the direction of the induced current in these coils is
A)clockwise in both coils.
B)counterclockwise in both coils.
C)clockwise in the east coil and counterclockwise in the west coil.
D)counterclockwise in the east coil and clockwise in the west coil.
A)clockwise in both coils.
B)counterclockwise in both coils.
C)clockwise in the east coil and counterclockwise in the west coil.
D)counterclockwise in the east coil and clockwise in the west coil.
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18
A coil lies flat on a horizontal tabletop in a region where the magnetic field points straight down.The magnetic field disappears suddenly.When viewed from above,what is the direction of the induced current in this coil as the field disappears?
A)counterclockwise
B)clockwise
C)clockwise initially,then counterclockwise before stopping
D)There is no induced current in this coil.
A)counterclockwise
B)clockwise
C)clockwise initially,then counterclockwise before stopping
D)There is no induced current in this coil.
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19
A coil of wire containing N turns is in an external magnetic field that is perpendicular to the plane of the coil and it steadily changing.Under these circumstances,an emf ε is induced in the coil.If the rate of change of the magnetic field and the number of turns in the coil are now doubled (but nothing else changes),what will be the induced emf in the coil?
A)2ε
B)ε/2
C)4ε
D)ε/4
E)ε
A)2ε
B)ε/2
C)4ε
D)ε/4
E)ε
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20
A flat coil is in a uniform magnetic field.The magnetic flux through the coil is greatest when the plane of its area is
A)parallel to the magnetic field.
B)at 45° with the magnetic field.
C)perpendicular to the magnetic field.
A)parallel to the magnetic field.
B)at 45° with the magnetic field.
C)perpendicular to the magnetic field.
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21
As shown in the figure,a battery supplies a steady current to the solenoid on the left.The two solenoids are moving toward each other with speeds v.The direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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22
As shown in the figure,a straight wire carries a current I into the page.The wire passes through the center of a toroidal coil.If the current I is quickly reduced to zero,the direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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23
As shown in the figure,two parallel wires carry a current I in opposite directions,and this current is decreasing.A rectangular loop is centered between the wires.The direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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24
A circular wire ring is situated above a long straight wire,as shown in the figure.The straight wire has a current I flowing to the right,and this current is increasing at a constant rate.Which of the following statements is true?
A)There is an induced current in the wire ring,directed in clockwise orientation.
B)There is an induced current in the wire ring,directed in a counterclockwise orientation.
C)There is no induced current in the wire ring.
A)There is an induced current in the wire ring,directed in clockwise orientation.
B)There is an induced current in the wire ring,directed in a counterclockwise orientation.
C)There is no induced current in the wire ring.
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25
A transformer is a device that normally
A)operates on either dc or ac.
B)operates only on ac.
C)operates only on dc.
A)operates on either dc or ac.
B)operates only on ac.
C)operates only on dc.
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26
As shown in the figure,a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν.A uniform magnetic field is present,directed downward as shown.The direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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27
As shown in the figure,two solenoids are side by side.The switch S is initially open.When S is suddenly closed,the direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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28
As shown in the figure,one end of a metal bar is in contact with a circular rail and the other end is pivoted at P.A steady uniform,magnetic field B into the page is present.As the bar rotates about point P in a clockwise direction,the direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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29
As shown in the figure,a C-shaped conductor is in a uniform magnetic field B out of the page,and this field is increasing.What is the polarity of the induced emf in terminals X and Y?
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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30
As shown in the figure,a metal bar is in contact with a pair of metal parallel rails.A steady uniform magnetic field B,perpendicular to the plane of the rails and pointing outward from the page,is present.The bar is in downward motion with velocity of magnitude ν.The direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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31
As shown in the figure,two solenoids are in line.The switch S,initially closed,is suddenly opened.Just after opening S,what is the polarity of the induced emf in terminals X and Y?
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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32
The wire in the figure carries a current I that is increasing with time at a constant rate.The wire and the three loops are all in the same plane.What is true about the currents induced in each of the three loops shown?
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
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33
The wire in the figure carries a current I that is decreasing with time at a constant rate.The wire and the three loops are all in the same plane.What is true about the currents induced in each of the three loops shown?
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
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34
If the secondary coil of a transformer contains more loops than the primary coil,then it is a
A)step-up transformer.
B)step-down transformer.
A)step-up transformer.
B)step-down transformer.
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35
A transformer is a device used to
A)transform an alternating current into a direct current.
B)transform a direct current into an alternating current.
C)increase or decrease an ac voltage.
D)increase or decrease a dc voltage.
A)transform an alternating current into a direct current.
B)transform a direct current into an alternating current.
C)increase or decrease an ac voltage.
D)increase or decrease a dc voltage.
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36
As shown in the figure,a metal bar is in contact with a pair of parallel rails.A steady,uniform,magnetic field B is present directed to the right.The bar is moving upward with velocity of magnitude ν.What is the polarity of the induced emf in terminals X and Y?
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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37
In the figure,a bar magnet moves away from the solenoid.The direction of the induced current through the resistor R is
A)from a to b.
B)from b to a.
C)No current is induced.
A)from a to b.
B)from b to a.
C)No current is induced.
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38
The wire in the figure carries a steady current I.What is true about the currents induced in each of the three loops shown? The wire and the three loops are all in the same plane.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
A)No current is induced in any loop.
B)The currents are counterclockwise in all three loops.
C)The currents are clockwise in all three loops.
D)Loop A has clockwise current,loop B has no induced current,and loop C has counterclockwise current.
E)Loop A has counterclockwise current,loop B has no induced current,and loop C has clockwise current.
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39
As shown in the figure,a coil of wire is placed in the xy-plane,centered on the z-axis.A solenoid is centered on the z-axis and is carrying a steady dc current.Which one of the following actions will not result induce an emf in the coil?
A)Rotate the coil about the x-axis.
B)Rotate the coil about the y-axis.
C)Rotate the coil about the z-axis.
D)Move the coil toward point P.
E)Change the current in the solenoid.
A)Rotate the coil about the x-axis.
B)Rotate the coil about the y-axis.
C)Rotate the coil about the z-axis.
D)Move the coil toward point P.
E)Change the current in the solenoid.
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40
As shown in the figure,a straight wire carries a steady current I.A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude ν.The polarity of the induced emf in terminals X and Y is
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
A)X and Y are at the same potential.
B)X is positive and Y is negative.
C)Y is positive and X is negative.
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41
A conductor is formed into a flat loop that encloses an area of
The plane of the loop is oriented at a 30.0° angle with the xy-plane.A uniform time-varying magnetic field is oriented parallel to the z-axis.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing?
A)29 T/s
B)22 T/s
C)50 T/s
D)13 T/s
The plane of the loop is oriented at a 30.0° angle with the xy-plane.A uniform time-varying magnetic field is oriented parallel to the z-axis.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing?
A)29 T/s
B)22 T/s
C)50 T/s
D)13 T/s
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42
A resistor and an inductor are connected in series to a battery.The time constant for the circuit represents the time required for the current to reach
A)25% of the maximum current.
B)37% of the maximum current.
C)63% of the maximum current.
D)75% of the maximum current.
E)100% of the maximum current.
A)25% of the maximum current.
B)37% of the maximum current.
C)63% of the maximum current.
D)75% of the maximum current.
E)100% of the maximum current.
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43
A bar magnet is pushed through a coil of wire of cross-sectional area 0.020 m2 as shown in the figure.The coil has seven turns,and the rate of change of the strength of the magnetic field in it due to the motion of the bar magnet is 0.040 T/s.What is the magnitude of the induced emf in that coil of wire?
A)5.6 × 10-3 V
B)5.6 × 10-2 V
C)5.6 × 10-1 V
D)5.6 × 10-4 V
E)5.6 × 10-5 V
A)5.6 × 10-3 V
B)5.6 × 10-2 V
C)5.6 × 10-1 V
D)5.6 × 10-4 V
E)5.6 × 10-5 V
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44
A flat circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T.Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are parallel.
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
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45
A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the resistor is
A)greater than the battery's terminal voltage.
B)equal to the battery's terminal voltage.
C)less than the battery's terminal voltage,but not zero.
D)zero.
E)equal to the voltage across the inductor.
A)greater than the battery's terminal voltage.
B)equal to the battery's terminal voltage.
C)less than the battery's terminal voltage,but not zero.
D)zero.
E)equal to the voltage across the inductor.
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46
A flat circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T.Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular.
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
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47
A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field?
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
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48
A circular coil of 20 turns and radius 5.0 cm is placed with its plane oriented at 90° to a uniform magnetic field of
The field is now increased at a steady rate,reaching a value of
After 4.0 seconds.What emf is induced in the coil?
A)0.016 V
B)0.021 V
C)0.026 V
D)0.031 V
E)0.036 V
The field is now increased at a steady rate,reaching a value of
After 4.0 seconds.What emf is induced in the coil?
A)0.016 V
B)0.021 V
C)0.026 V
D)0.031 V
E)0.036 V
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49
If the primary coil of a transformer contains more loops than the secondary coil then it is a
A)step-up transformer.
B)step-down transformer.
A)step-up transformer.
B)step-down transformer.
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50
A resistor and an inductor are connected in series to a battery.The battery is suddenly removed from the circuit and replaced by a wire to complete the circuit.The time constant for of the new circuit represents the time required for the current to decrease to
A)25% of the original value.
B)37% of the original value.
C)63% of the original value.
D)75% of the original value.
E)zero.
A)25% of the original value.
B)37% of the original value.
C)63% of the original value.
D)75% of the original value.
E)zero.
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51
A flat circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T.Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are at an angle of 30°.
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
A)0 T ∙ m2
B)3.1 × 10-3 T ∙ m2
C)5.5 × 10-3 T ∙ m2
D)6.3 × 10-3 T ∙ m2
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52
A closed flat loop conductor with radius
Is located in a changing uniform magnetic field.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?
A)0.16 T/s
B)1.0 T/s
C)0.080 T/s
D)2.0 T/s
Is located in a changing uniform magnetic field.If the emf induced in the loop is
What is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?
A)0.16 T/s
B)1.0 T/s
C)0.080 T/s
D)2.0 T/s
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53
A circular conducting loop with a radius of
And a small gap filled with a
Resistor is oriented in the
If a uniform magnetic field of
Making an angle of
With the
Increases to
In
What is the magnitude of the current that will be caused to flow in the loop if it has negligible resistance?
A)0.01530393 A
B)0.08835729 A
C)0.15303932 A
D)0 A
And a small gap filled with a
Resistor is oriented in the
If a uniform magnetic field of
Making an angle of
With the
Increases to
In
What is the magnitude of the current that will be caused to flow in the loop if it has negligible resistance?
A)0.01530393 A
B)0.08835729 A
C)0.15303932 A
D)0 A
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54
A 2.00-m long metal wire is formed into a square and placed in the horizontal xy-plane.A uniform magnetic field is oriented at 30° above the horizontal with a strength of 0.344 T.What is the magnetic flux through the square due to this field?
A)0.0745 T ∙ m2
B)0.172 T ∙ m2
C)0.0430 T ∙ m2
D)0.298 T ∙ m2
A)0.0745 T ∙ m2
B)0.172 T ∙ m2
C)0.0430 T ∙ m2
D)0.298 T ∙ m2
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55
The magnetic flux through a coil changes steadily from 4.0 × 10-5 T ∙ m2 to 5.0 × 10-5 T ∙ m2 in 0.10 s.What emf is induced in this coil?
A)5.0 × 10-4 V
B)4.0 × 10-4 V
C)1.0 × 10-4 V
D)None of the given answers are correct.
A)5.0 × 10-4 V
B)4.0 × 10-4 V
C)1.0 × 10-4 V
D)None of the given answers are correct.
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56
A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop makes an angle of 60° with the magnetic field?
A)2.6 × 10-3 T ∙ m2
B)1.3 × 10-3 T ∙ m2
C)0 T ∙ m2
D)2.2 × 10-3 T ∙ m2
E)0.80 T ∙ m2
A)2.6 × 10-3 T ∙ m2
B)1.3 × 10-3 T ∙ m2
C)0 T ∙ m2
D)2.2 × 10-3 T ∙ m2
E)0.80 T ∙ m2
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57
A flux of 4.0 × 10-5 T ∙ m2 is maintained through a coil of area 7.5 cm2 for 0.50 s.What emf is induced in this coil during this time by this flux?
A)8.0 × 10-5 V
B)4.0 × 10-5 V
C)3.0 × 10-5 V
D)2.0 × 10-5 V
E)No emf is induced in this coil.
A)8.0 × 10-5 V
B)4.0 × 10-5 V
C)3.0 × 10-5 V
D)2.0 × 10-5 V
E)No emf is induced in this coil.
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58
A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the inductor is
A)greater than the battery's terminal voltage.
B)equal to the battery's terminal voltage.
C)less than the battery's terminal voltage,but not zero.
D)zero.
E)equal to the voltage across the resistor.
A)greater than the battery's terminal voltage.
B)equal to the battery's terminal voltage.
C)less than the battery's terminal voltage,but not zero.
D)zero.
E)equal to the voltage across the resistor.
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59
A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T,as shown in the figure.The length of the loop L is 0.16 m and its width w is 0.040 m.What is the magnetic flux through the loop when the plane of the loop is perpendicular to the magnetic field?
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
A)13 × 10-3 T ∙ m2
B)2.6 × 103 T ∙ m2
C)0.80 T ∙ m2
D)2.6 × 10-3 T ∙ m2
E)0 T ∙ m2
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60
An ideal solenoid has a self-inductance L.If you now double its radius and its length,but do not change the number of coils,what will its self-inductance be?
A)4L
B)2L
C)L
D)L/2
E)L/4
A)4L
B)2L
C)L
D)L/2
E)L/4
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61
A conducting rod whose length is ℓ = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper.What is the magnitude of the external applied force needed to move the rod to the right with a constant speed of 6.00 m/s?
A)8.60 N
B)9.30 N
C)10.6 N
D)12.6 N
E)18.6 N
A)8.60 N
B)9.30 N
C)10.6 N
D)12.6 N
E)18.6 N
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62
It is known that birds can detect the earth's magnetic field,but the mechanism of how they do this is not known.It has been suggested that perhaps they detect a motional emf as they fly north to south,but it turns out that the induced voltages are small compared to the voltages normally encountered in cells,so this is probably not the mechanism involved.To check this out,calculate the induced voltage across the wingtips of a wild goose with a wingspan of
If it is flying directly south at
At a point where the earth's magnetic field is 5.0 × 10-5 T directed downward from the horizontal by
A)0.50 mV
B)0.60 mV
C)0.78 mV
D)0.060 mV
E)0.25 mV
If it is flying directly south at
At a point where the earth's magnetic field is 5.0 × 10-5 T directed downward from the horizontal by
A)0.50 mV
B)0.60 mV
C)0.78 mV
D)0.060 mV
E)0.25 mV
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63
A flat square coil of wire with 15 turns and an area of 0.40 m2 is placed with the plane of its area parallel to a magnetic field of 0.75 T.The coil is flipped so its plane is perpendicular to the magnetic field in a time of 0.050 s.What is the magnitude of the average induced emf in the coil?
A)6.0 V
B)36 V
C)45 V
D)90 V
A)6.0 V
B)36 V
C)45 V
D)90 V
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64
A flat coil is wrapped with 200 turns of very thin wire on a square frame with sides 18 cm long.A uniform magnetic field is applied perpendicular to the plane of the coil.If the field changes uniformly from 0.50 T to 0.00 T in 8.0 s,find the emf induced in the coil.
A)2.1 mV
B)4.1 mV
C)0.21 V
D)0.41 V
A)2.1 mV
B)4.1 mV
C)0.21 V
D)0.41 V
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65
A conducting rod whose length is ℓ = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the right with a constant speed of 6.00 m/s.At what rate is energy dissipated in the lightbulb?
A)60.0 W
B)121 W
C)21.2 W
D)112 W
E)11.5 W
A)60.0 W
B)121 W
C)21.2 W
D)112 W
E)11.5 W
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66
A flat rectangular coil with dimensions of 8.0 cm × 10 cm is dropped from a zero magnetic field position into a 1.4-T magnetic field in 0.10 s.The coil has 60 turns and is perpendicular to the magnetic field.What is the average induced emf in the coil as a result of this action?
A)8.6 V
B)2.4 V
C)6.7 V
D)3.6 V
E)0 V
A)8.6 V
B)2.4 V
C)6.7 V
D)3.6 V
E)0 V
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67
A round flat metal coil has 180 turns and negligible resistance.It is connected in a series circuit with a
Resistor,with nothing else in the circuit.You measure that a
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at
What is the radius of the coil?
A)0.25 m
B)0.014 m
C)0.54 m
D)0.043 m
Resistor,with nothing else in the circuit.You measure that a
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at
What is the radius of the coil?
A)0.25 m
B)0.014 m
C)0.54 m
D)0.043 m
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68
A round flat conducting loop is placed perpendicular to a uniform 0.50 T magnetic field.If the area of the loop increases at a rate of 3.0 ×
/s,what is the induced emf in the loop?
A)4.3 mV
B)0 mV
C)1.5 mV
D)1.7 mV
E)5.5 mV
/s,what is the induced emf in the loop?
A)4.3 mV
B)0 mV
C)1.5 mV
D)1.7 mV
E)5.5 mV
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69
A flat coil having 160 turns,each with an area of 0.20 m2,is placed with the plane of its area perpendicular to a magnetic field of 0.40 T.The magnetic field changes uniformly from 0.40 T in the +x direction to 0.40 T in the -x direction in 2.0 s.If the resistance of the coil is 16 Ω,at what rate is power generated in the coil during this change?
A)5.0 W
B)10 W
C)15 W
D)20 W
A)5.0 W
B)10 W
C)15 W
D)20 W
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70
A long vertical wire carries a steady 70 A current.As shown in the figure,a pair of horizontal rails are 0.20 m apart.A 20-Ω resistor connects points a and b,at the end of the rails.A bar is in contact with the rails,and is moved by an external force with a constant horizontal velocity of 0.90 m/s to the right,as shown.The bar and the rails have negligible resistance.At the instant that the bar is 0.20 m from the wire,what are the induced current in the resistor and its direction through the resistor? (μ0 = 4π × 10-7 T ∙ m/A)
A)0.63 μA,from a to b
B)0.63 μA,from b to a
C)0.32 μA,from a to b
D)0.32 μA,from b to a
E)1.9 μA,from b to a
A)0.63 μA,from a to b
B)0.63 μA,from b to a
C)0.32 μA,from a to b
D)0.32 μA,from b to a
E)1.9 μA,from b to a
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71
An electromagnetic flowmeter is useful when it is desirable not to interrupt the system in which the fluid is flowing (such as the blood in an artery during heart surgery).Such a device is illustrated in the figure.The conducting fluid moves with speed v in a tube of diameter d.Perpendicular to this tube is a magnetic field B.A voltage V is induced between opposite sides of the tube due to the motion of the conducting fluid in the magnetic field.For a certain case,B = 0.120 T,d = 1.2 cm,and the measured voltage is
Determine the speed of the fluid.
A)2.0 m/s
B)11 m/s
C)0.075 m/s
D)1.1 m/s
E)750 m/s
Determine the speed of the fluid.
A)2.0 m/s
B)11 m/s
C)0.075 m/s
D)1.1 m/s
E)750 m/s
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72
A conducting rod whose length is ℓ = 27.0 cm is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 5.00 Ω as shown in the figure.The rails and the rod are in the plane of the page.A constant uniform magnetic field of strength 1.20 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the right with a constant speed.At what speed should the rod be pulled so that the lightbulb will consume energy at a rate of 1.10 W?
A)2.00 m/s
B)3.50 m/s
C)4.26 m/s
D)6.00 m/s
E)7.24 m/s
A)2.00 m/s
B)3.50 m/s
C)4.26 m/s
D)6.00 m/s
E)7.24 m/s
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73
A conducting rod with a length ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and into the paper.An external applied force moves the rod to the right with a constant speed of 6.0 m/s.What are the magnitude and direction of the induced current in the circuit?
A)17 mA clockwise
B)17 mA counterclockwise
C)75 mA counterclockwise
D)75 mA clockwise
E)52 mA clockwise
A)17 mA clockwise
B)17 mA counterclockwise
C)75 mA counterclockwise
D)75 mA clockwise
E)52 mA clockwise
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74
A single-turn loop of wire,having a resistance of 8.00 Ω and a cross-sectional area 200 cm2,is perpendicular to a uniform magnetic field that increases steadily from 0.200 T to 2.800 T in 2.20 seconds.What is the magnitude of the induced current in the loop?
A)2.95 A
B)3.18 A
C)0 A
D)3.18 mA
E)2.95 mA
A)2.95 A
B)3.18 A
C)0 A
D)3.18 mA
E)2.95 mA
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75
The primary coil of an ideal transformer has 100 turns and its secondary coil has 400 turns.If the ac voltage applied to the primary coil is 120 V,what voltage is present in its secondary coil?
A)100 V
B)30 V
C)70 V
D)480 V
E)400 V
A)100 V
B)30 V
C)70 V
D)480 V
E)400 V
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76
The area of a rectangular loop of wire is 3.6 ×
.The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?
A)2.8 × V
B)2.7 × V
C)0 V
D)1.8 × V
E)3.0 × V
.The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?
A)2.8 ×
VB)2.7 ×
VC)0 V
D)1.8 ×
VE)3.0 ×
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77
As shown in the figure,a wire and a 10-Ω resistor are used to form a circuit in the shape of a square with dimensions 20 cm by 20 cm.A uniform but non-steady magnetic field is directed into the plane of the circuit.The magnitude of the magnetic field is steadily decreased from 2.70 T to 0.90 T in a time interval of 96 ms.What is the induced current in the circuit,and what is its direction through the resistor?
A)75 mA,from b to a
B)45 mA,from b to a
C)75 mA,from a to b
D)45 mA,from a to b
E)110 mA,from a to b
A)75 mA,from b to a
B)45 mA,from b to a
C)75 mA,from a to b
D)45 mA,from a to b
E)110 mA,from a to b
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78
A conducting rod of length ℓ= 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω,as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and into the paper.An applied external force pulls the rod to the right with a constant speed of 6.0 m/s.What is the magnitude of the emf induced in the rod?
A)0.20 V
B)0.30 V
C)0.40 V
D)0.50 V
E)0.60 V
A)0.20 V
B)0.30 V
C)0.40 V
D)0.50 V
E)0.60 V
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79
A constant uniform magnetic field of 0.50 T is applied at right angles to the plane of a flat rectangular loop of area 3.0 ×
.If the area of this loop changes steadily from its original value to a new value of 1.6 × 10-3 m2 in 1.6 s,what is the emf induced in the loop?
A)1.6 × V
B)0 V
C)7.5 × V
D)4.4 × V
E)9.0 × V
.If the area of this loop changes steadily from its original value to a new value of 1.6 × 10-3 m2 in 1.6 s,what is the emf induced in the loop?
A)1.6 ×
VB)0 V
C)7.5 ×
VD)4.4 ×
VE)9.0 ×
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80
A conducting rod whose length is ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and out of the paper.An external applied force moves the rod to the left with a constant speed of 12 m/s.What are the magnitude and direction of the induced current in the circuit?
A)150 mA clockwise
B)150 mA counterclockwise
C)34 mA counterclockwise
D)34 mA clockwise
E)100 mA clockwise
A)150 mA clockwise
B)150 mA counterclockwise
C)34 mA counterclockwise
D)34 mA clockwise
E)100 mA clockwise
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