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Deck 23: Magnetic Flux and Faradays Law of Induction
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FIGURE 23-1 
The three loops of wire shown in Figure 23-1 are all subject to the same uniform magnetic field
that does not vary with time. Loop 1 oscillates back and forth as 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 induced emf?
A) Loop 1
B) Loop 2
C) Loop 3
D) Loops 1 and 3
E) Loops 2 and 3
The three loops of wire shown in Figure 23-1 are all subject to the same uniform magnetic field
that does not vary with time. Loop 1 oscillates back and forth as 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 induced emf?A) Loop 1
B) Loop 2
C) Loop 3
D) Loops 1 and 3
E) Loops 2 and 3
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FIGURE 23-2 
The two identical bar magnets in Figure 23-2 are dropped from rest along a vertical line passing through the center of the rings, as shown. The two rings are identical in every respect except that the ring on the right has a small break in it. Calling aL and aR the magnitude of the downward accelerations of the magnets on the left and right, respectively, you observe that
A) aL = aR.
B) aL > aR.
C) aL < aR.
D) It is not possible to predict the outcome of this experiment with the data given.
The two identical bar magnets in Figure 23-2 are dropped from rest along a vertical line passing through the center of the rings, as shown. The two rings are identical in every respect except that the ring on the right has a small break in it. Calling aL and aR the magnitude of the downward accelerations of the magnets on the left and right, respectively, you observe that
A) aL = aR.
B) aL > aR.
C) aL < aR.
D) It is not possible to predict the outcome of this experiment with the data given.
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FIGURE 23-4 
A rectangular coil with N turns, length L, and width w, as shown in Figure 23-4, is rotating in a magnetic field B with an angular frequency ω. If the area of the coil is A, what is the induced emf in the coil?
A) ε = NB (Lw) ω sin ωt
B) ε = NBA ω sin ωt
C) ε = NBA (2πf) sin 2πft
D) All of these answers are correct.
E) None of these answers is correct.
A rectangular coil with N turns, length L, and width w, as shown in Figure 23-4, is rotating in a magnetic field B with an angular frequency ω. If the area of the coil is A, what is the induced emf in the coil?
A) ε = NB (Lw) ω sin ωt
B) ε = NBA ω sin ωt
C) ε = NBA (2πf) sin 2πft
D) All of these answers are correct.
E) None of these answers is correct.
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FIGURE 23-3 
The wire in Figure 23-3 carries a current I that is increasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
The wire in Figure 23-3 carries a current I that is increasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
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FIGURE 23-3
The wire in Figure 23-3 carries a current I that is decreasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
The wire in Figure 23-3 carries a current I that is decreasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
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FIGURE 23-5 
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field whose strength is 0.40 T, as shown in Figure 23-5. The length of the loop L is 0.16 m and its width w is 0.04 m. What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field?
A) -2.6 × 10-3 T∙m2
B) +2.6 × 10-3 T∙m2
C) 0 T∙m2
D) -1.3 × 10-3 T∙m2
E) 1.3 × 10-3 T∙m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field whose strength is 0.40 T, as shown in Figure 23-5. The length of the loop L is 0.16 m and its width w is 0.04 m. What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field?
A) -2.6 × 10-3 T∙m2
B) +2.6 × 10-3 T∙m2
C) 0 T∙m2
D) -1.3 × 10-3 T∙m2
E) 1.3 × 10-3 T∙m2
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FIGURE 23-5
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field with a strength of 0.40 T as shown in Figure 23-5. 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 × 10-3 T∙ m2
C) 0.80 T∙ m2
D) 2.6 × 10-3 T∙ m2
E) 0 T∙ m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field with a strength of 0.40 T as shown in Figure 23-5. 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 × 10-3 T∙ m2
C) 0.80 T∙ m2
D) 2.6 × 10-3 T∙ m2
E) 0 T∙ m2
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FIGURE 23-6 
A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10-3 m2/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
A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10-3 m2/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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FIGURE 23-7 
A bar magnet with its north pole pointing toward a coil of wire with a cross-sectional area of 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-7(b). If the rate of change in the strength of the magnetic field caused by the motion of the bar magnet is 0.040 T/s, what is the direction of the induced emf in the coil of wire (when looking at the end of the coil where the N pole is coming toward you)?
A) counterclockwise
B) clockwise
C) No emf is induced.
A bar magnet with its north pole pointing toward a coil of wire with a cross-sectional area of 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-7(b). If the rate of change in the strength of the magnetic field caused by the motion of the bar magnet is 0.040 T/s, what is the direction of the induced emf in the coil of wire (when looking at the end of the coil where the N pole is coming toward you)?
A) counterclockwise
B) clockwise
C) No emf is induced.
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FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the shaded face of the cube?
A) 4.0 × 10-1 T∙m2
B) 4.0 × 10-2 T∙m2
C) 4.0 × 10-3 T∙m2
D) 4.0 × 10-4 T∙m2
E) 0 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the shaded face of the cube?
A) 4.0 × 10-1 T∙m2
B) 4.0 × 10-2 T∙m2
C) 4.0 × 10-3 T∙m2
D) 4.0 × 10-4 T∙m2
E) 0 T∙m2
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FIGURE 23-8 
A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?
A) 7.2 V
B) 5.4 V
C) 9.2 V
D) 12 V
E) 0 V
A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?
A) 7.2 V
B) 5.4 V
C) 9.2 V
D) 12 V
E) 0 V
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FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the face of the cube along the y-z plane at x = 0?
A) 4.0 × 10-2 T∙m2
B) -4.0 × 10-3 T∙m2
C) -4.0 × 10-2 T∙m2
D) 4.0 × 10-3 T∙m2
E) 0 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the face of the cube along the y-z plane at x = 0?
A) 4.0 × 10-2 T∙m2
B) -4.0 × 10-3 T∙m2
C) -4.0 × 10-2 T∙m2
D) 4.0 × 10-3 T∙m2
E) 0 T∙m2
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FIGURE 23-5
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field of strength 0.40 T as shown in Figure 23-5. 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) -1.3 × 10-3 T∙m2
B) 1.3 × 10-3 T∙m2
C) 0 T∙m2
D) -2.6 × 10-3 T∙m2
E) 2.6 × 10-3 T∙m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field of strength 0.40 T as shown in Figure 23-5. 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) -1.3 × 10-3 T∙m2
B) 1.3 × 10-3 T∙m2
C) 0 T∙m2
D) -2.6 × 10-3 T∙m2
E) 2.6 × 10-3 T∙m2
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FIGURE 23-8
A constant magnetic field is applied perpendicular to the plane of a square, single-turn coil with each side equal to 15 cm. If the area of the coil decreases at a rate of 0.20 m2/s, an emf of 20 mV is induced in that coil. What is the strength of the magnetic field applied to the coil?
A) 0.10 T
B) 0.20 T
C) 0.30 T
D) 0.40 T
E) 0.50 T
A constant magnetic field is applied perpendicular to the plane of a square, single-turn coil with each side equal to 15 cm. If the area of the coil decreases at a rate of 0.20 m2/s, an emf of 20 mV is induced in that coil. What is the strength of the magnetic field applied to the coil?
A) 0.10 T
B) 0.20 T
C) 0.30 T
D) 0.40 T
E) 0.50 T
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FIGURE 23-8
A single-turn plane loop of wire with a cross-sectional area 200 cm2 is perpendicular to a magnetic field that increases uniformly from 0.200 T to 2.800 T in 2.20 seconds. What is the magnitude of the induced current if the resistance of the coil is 8.00 Ω?
A) 2.95 A
B) 3.18 A
C) 0 A
D) 3.18 mA
E) 2.95 mA
A single-turn plane loop of wire with a cross-sectional area 200 cm2 is perpendicular to a magnetic field that increases uniformly from 0.200 T to 2.800 T in 2.20 seconds. What is the magnitude of the induced current if the resistance of the coil is 8.00 Ω?
A) 2.95 A
B) 3.18 A
C) 0 A
D) 3.18 mA
E) 2.95 mA
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FIGURE 23-8
A bar magnet with its south pole pointing toward a loop of wire of cross-sectional area 0.020 m2 and total number of turns equal to six is stationary near the loop of wire shown in Figure 23-8(a). What is the direction of the induced emf in that loop of wire (when looking at the end of the coil where the S pole is coming toward you)?
A) clockwise
B) counterclockwise
C) There is no emf induced.
A bar magnet with its south pole pointing toward a loop of wire of cross-sectional area 0.020 m2 and total number of turns equal to six is stationary near the loop of wire shown in Figure 23-8(a). What is the direction of the induced emf in that loop of wire (when looking at the end of the coil where the S pole is coming toward you)?
A) clockwise
B) counterclockwise
C) There is no emf induced.
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FIGURE 23-10 
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance of 8.0 Ω as shown in Figure 23-10. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied out of the paper. An applied force moves the rod to the left with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 75 mA clockwise
B) 75 mA counterclockwise
C) 17 mA counterclockwise
D) 17 mA clockwise
E) 52 mA clockwise
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance of 8.0 Ω as shown in Figure 23-10. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied out of the paper. An applied force moves the rod to the left with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 75 mA clockwise
B) 75 mA counterclockwise
C) 17 mA counterclockwise
D) 17 mA clockwise
E) 52 mA clockwise
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FIGURE 23-8
A bar magnet with its south pole pointing toward a coil of wire of cross-sectional area 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-8(b). If the rate of change in the strength of the magnetic field caused by 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 bar magnet with its south pole pointing toward a coil of wire of cross-sectional area 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-8(b). If the rate of change in the strength of the magnetic field caused by 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
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FIGURE 23-9 
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ω as shown in Figure 23-9. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s. What is the magnitude of the induced emf in the wire?
A) 0.2 V
B) 0.3 V
C) 0.4 V
D) 0.5 V
E) 0.6 V
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ω as shown in Figure 23-9. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s. What is the magnitude of the induced emf in the wire?
A) 0.2 V
B) 0.3 V
C) 0.4 V
D) 0.5 V
E) 0.6 V
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FIGURE 23-9
A conducting rod with a length of 25 cm is placed on a U-shaped metal wire that has a resistance R of 8.0 Ω as shown in Figure 23-9. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied perpendicular into the paper. An applied force moves the rod to the right with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 17 mA clockwise
B) 17 mA counterclockwise
C) 75 mA counterclockwise
D) 75 mA clockwise
E) 52 mA clockwise
A conducting rod with a length of 25 cm is placed on a U-shaped metal wire that has a resistance R of 8.0 Ω as shown in Figure 23-9. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied perpendicular into the paper. An applied force moves the rod to the right with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 17 mA clockwise
B) 17 mA counterclockwise
C) 75 mA counterclockwise
D) 75 mA clockwise
E) 52 mA clockwise
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FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field of strength 0.40 T is applied along the +x-axis. What is the total magnetic flux through the six faces of the cube?
A) 0 T∙m2
B) -4.0 × 10-3 T∙m2
C) +4.0 × 10-2 T∙m2
D) -4.0 × 10-2 T∙m2
E) 4.0 × 10-3 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field of strength 0.40 T is applied along the +x-axis. What is the total magnetic flux through the six faces of the cube?
A) 0 T∙m2
B) -4.0 × 10-3 T∙m2
C) +4.0 × 10-2 T∙m2
D) -4.0 × 10-2 T∙m2
E) 4.0 × 10-3 T∙m2
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FIGURE 23-7
A bar magnet is placed with its north pole pointing toward a coil of wire that has a cross-sectional area of 0.02 m2 and 6 turns, as shown in Figure 23-7(a). What is the magnitude of the induced emf in the coil of wire?
A) 0.04 V
B) 0.03 V
C) 0.01 V
D) 0.02 V
E) 0 V
A bar magnet is placed with its north pole pointing toward a coil of wire that has a cross-sectional area of 0.02 m2 and 6 turns, as shown in Figure 23-7(a). What is the magnitude of the induced emf in the coil of wire?
A) 0.04 V
B) 0.03 V
C) 0.01 V
D) 0.02 V
E) 0 V
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Deck 23: Magnetic Flux and Faradays Law of Induction
1
According to Lenz's Law, the direction of the induced current in a conducting loop of wire is that which tends to oppose the change that produces it.
True
2
An emf is induced in a wire by keeping a stationary magnet near the wire.
False
3
The negative sign in the Faraday's equation for electromagnetic induction is related to the direction of the induced emf.
True
4
An emf is induced in a wire by changing the current in a nearby wire.
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5
A constant current I in a coil of inductance L does not produce an emf in that coil.
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6
An emf is induced in a wire by moving the wire near a magnet.
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7
If the rate of change of the magnetic field applied to a loop of wire is doubled, what happens to the induced emf in that loop assuming all the other parameters remain unchanged?
A) It is doubled.
B) It stays the same.
C) It is reduced by a factor of 2.
D) It is quadrupled.
E) It is reduced by a factor of 4.
A) It is doubled.
B) It stays the same.
C) It is reduced by a factor of 2.
D) It is quadrupled.
E) It is reduced by a factor of 4.
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8
There is an induced emf in a wire that is moving parallel to a magnetic field if the wire is moving in the opposite direction to that of the magnetic field.
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9
FIGURE 23-1
The three loops of wire shown in Figure 23-1 are all subject to the same uniform magnetic field that does not vary with time. Loop 1 oscillates back and forth as 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 induced emf?
A) Loop 1
B) Loop 2
C) Loop 3
D) Loops 1 and 3
E) Loops 2 and 3
The three loops of wire shown in Figure 23-1 are all subject to the same uniform magnetic field
that does not vary with time. Loop 1 oscillates back and forth as 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 induced emf?A) Loop 1
B) Loop 2
C) Loop 3
D) Loops 1 and 3
E) Loops 2 and 3
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10
If the number of turns in a rectangular coil of wire that is rotating in a magnetic field is doubled, what happens to the induced emf, assuming all the other variables remain the same?
A) It stays the same.
B) It is reduced by a factor of 4.
C) It is reduced by a factor of 2.
D) It is doubled.
E) It is quadrupled.
A) It stays the same.
B) It is reduced by a factor of 4.
C) It is reduced by a factor of 2.
D) It is doubled.
E) It is quadrupled.
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11
For the maximum induced emf in the coil of a generator, the term sin ωt has a value of one.
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12
A changing magnetic flux through a closed loop of wire induces an emf in that loop.
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13
The emf in a conducting rod of length L moving perpendicular to a magnetic field is directly proportional to the speed of the rod.
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14
If the strength of the magnetic field applied to a loop of wire is doubled, what happens to the induced emf in that loop assuming all the other parameters remain unchanged?
A) It stays the same.
B) It is doubled.
C) It is tripled.
D) It is quadrupled.
E) It is reduced by a factor of 2.
A) It stays the same.
B) It is doubled.
C) It is tripled.
D) It is quadrupled.
E) It is reduced by a factor of 2.
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15
State Lenz's Law.
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16
For the maximum induced emf in the coil of a generator, the term sin ωt has a value of zero.
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17
An emf is induced in a wire by changing the current in that wire.
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18
The shape of the wire determines the direction of the induced current in a conducting loop of wire.
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19
There is no induced emf in a wire that is moving parallel to a magnetic field if the wire is moving in the direction of the magnetic field.
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20
A constant magnetic flux through a closed loop of wire induces an emf in that loop.
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21
A transformer is based on a principle of
A) self inductance.
B) direct current.
C) alternating current.
D) mutual inductance.
E) energy conservation.
A) self inductance.
B) direct current.
C) alternating current.
D) mutual inductance.
E) energy conservation.
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22
FIGURE 23-2
The two identical bar magnets in Figure 23-2 are dropped from rest along a vertical line passing through the center of the rings, as shown. The two rings are identical in every respect except that the ring on the right has a small break in it. Calling aL and aR the magnitude of the downward accelerations of the magnets on the left and right, respectively, you observe that
A) aL = aR.
B) aL > aR.
C) aL < aR.
D) It is not possible to predict the outcome of this experiment with the data given.
The two identical bar magnets in Figure 23-2 are dropped from rest along a vertical line passing through the center of the rings, as shown. The two rings are identical in every respect except that the ring on the right has a small break in it. Calling aL and aR the magnitude of the downward accelerations of the magnets on the left and right, respectively, you observe that
A) aL = aR.
B) aL > aR.
C) aL < aR.
D) It is not possible to predict the outcome of this experiment with the data given.
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23
The magnetic field and the number of turns of a coil of wire are doubled, while its area is reduced by a factor of 2. Assuming that all the other parameters remain the same, what happens to the induced emf in that coil of wire?
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is quadrupled.
D) It is reduced by a factor of 4.
E) It stays the same.
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is quadrupled.
D) It is reduced by a factor of 4.
E) It stays the same.
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24
Which of the following is true for the SI units of self-inductance?
A) Ω∙s
B) henry (H)
C) (J∙s)/(C∙A)
D) All are correct answers.
E) None are correct answers.
A) Ω∙s
B) henry (H)
C) (J∙s)/(C∙A)
D) All are correct answers.
E) None are correct answers.
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25
The number of turns in the coil of a generator is reduced by a factor of 2 and at the same time it is rotated twice as fast keeping other factors constant. What happens to the value of the maximum induced emf?
A) It is reduced by a factor of 2.
B) It is reduced by a factor of 4.
C) It is doubled.
D) It stays the same.
E) It is quadrupled.
A) It is reduced by a factor of 2.
B) It is reduced by a factor of 4.
C) It is doubled.
D) It stays the same.
E) It is quadrupled.
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26
A rectangular coil lies flat on a horizontal surface. A bar magnet is held above the center of the coil with its north pole pointing down. What is the direction of the induced current in the coil?
A) There is no current in the coil.
B) clockwise
C) counterclockwise
D) Not enough information is provided.
A) There is no current in the coil.
B) clockwise
C) counterclockwise
D) Not enough information is provided.
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27
Which one of the following is the correct unit for the time constant of an RL circuit?
A) H/Ω
B) (V∙s)/(A∙Ω)
C) s
D) All of the answers are correct.
E) None of the answers is correct.
A) H/Ω
B) (V∙s)/(A∙Ω)
C) s
D) All of the answers are correct.
E) None of the answers is correct.
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28
A rectangular 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?
A) There is no current in the coil.
B) counterclockwise
C) clockwise
D) Not enough information is provided.
A) There is no current in the coil.
B) counterclockwise
C) clockwise
D) Not enough information is provided.
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29
The area of a loop of wire is reduced by a factor of 2 while the rate of change of magnetic field applied is doubled. What happens to the induced emf in that loop of wire?
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is reduced by a factor of 4.
D) It is quadrupled.
E) It stays the same.
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is reduced by a factor of 4.
D) It is quadrupled.
E) It stays the same.
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30
The magnetic field and the number of turns in a coil of wire are doubled. Assuming that all the other parameters remain the same, what happens to the induced emf in that coil of wire?
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is quadrupled.
D) It is reduced by a factor of 4.
E) It stays the same.
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is quadrupled.
D) It is reduced by a factor of 4.
E) It stays the same.
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31
The coil of a generator is rotated twice as fast keeping all other factors constant. What happens to the value of the maximum induced emf?
A) It stays the same.
B) It is reduced by a factor of 2.
C) It is increased by a factor of 2.
D) It is increased by a factor of 4.
E) It is reduced by a factor of 4.
A) It stays the same.
B) It is reduced by a factor of 2.
C) It is increased by a factor of 2.
D) It is increased by a factor of 4.
E) It is reduced by a factor of 4.
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32
A circular loop of one turn and radius 5.0 cm is positioned with its axis parallel to a magnetic field of 0.60 T. By means of high explosives, the area of the loop is suddenly reduced to essentially zero in 0.50 ms. What emf is induced in the loop?
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33
The energy stored in a coil of self-inductance, L, and traversed by current I, is E1. A second coil is made with the same length of wire, but its radius is twice the radius of the first coil and it is twice as long as the first coil. If the second coil also has twice the current of the first coil, how does the energy stored in the first coil, E1, compare to the energy stored in the second coil, E2?
A) E1 = E2
B) E1 = E2/8
C) E1 = 4E2
D) E1 = E2/2
E) E1 = E2/4
A) E1 = E2
B) E1 = E2/8
C) E1 = 4E2
D) E1 = E2/2
E) E1 = E2/4
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34
How would the self-inductance, L, of a coil change if you would increase its radius by a factor of two and increase its length by a factor of two?
A) L would not change.
B) L would be doubled.
C) L would be quadrupled.
D) L would be halved.
E) L would be reduced by 4.
A) L would not change.
B) L would be doubled.
C) L would be quadrupled.
D) L would be halved.
E) L would be reduced by 4.
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35
The area and the number of turns in a loop of wire are doubled. Assuming that all the other parameters remain the same, what happens to the induced emf in that loop of wire?
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is reduced by a factor of 4.
D) It is quadrupled.
E) It stays the same.
A) It is doubled.
B) It is reduced by a factor of 2.
C) It is reduced by a factor of 4.
D) It is quadrupled.
E) It stays the same.
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36
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is kept stationary with respect to the coil. As viewed from above, you can say that the magnet induces
A) counterclockwise current in the loop.
B) clockwise current in the loop.
C) no current in the loop.
D) an emf but no electric current in the loop.
E) Not enough information is provided.
A) counterclockwise current in the loop.
B) clockwise current in the loop.
C) no current in the loop.
D) an emf but no electric current in the loop.
E) Not enough information is provided.
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37
FIGURE 23-4
A rectangular coil with N turns, length L, and width w, as shown in Figure 23-4, is rotating in a magnetic field B with an angular frequency ω. If the area of the coil is A, what is the induced emf in the coil?
A) ε = NB (Lw) ω sin ωt
B) ε = NBA ω sin ωt
C) ε = NBA (2πf) sin 2πft
D) All of these answers are correct.
E) None of these answers is correct.
A rectangular coil with N turns, length L, and width w, as shown in Figure 23-4, is rotating in a magnetic field B with an angular frequency ω. If the area of the coil is A, what is the induced emf in the coil?
A) ε = NB (Lw) ω sin ωt
B) ε = NBA ω sin ωt
C) ε = NBA (2πf) sin 2πft
D) All of these answers are correct.
E) None of these answers is correct.
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38
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is released from rest and falls toward the coil. As viewed from above, you can say that, as it falls, the magnet induces
A) counterclockwise current in the loop.
B) clockwise current in the loop.
C) no current in the loop.
D) an emf but no electric current in the loop.
E) Not enough information is provided.
A) counterclockwise current in the loop.
B) clockwise current in the loop.
C) no current in the loop.
D) an emf but no electric current in the loop.
E) Not enough information is provided.
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39
FIGURE 23-3
The wire in Figure 23-3 carries a current I that is increasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
The wire in Figure 23-3 carries a current I that is increasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
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40
FIGURE 23-3
The wire in Figure 23-3 carries a current I that is decreasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
The wire in Figure 23-3 carries a current I that is decreasing with time at a constant rate. The induced emf in each of the loops is such that
A) no emf is induced in any loop.
B) all loops experience counterclockwise emf.
C) loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
D) loop A has counterclockwise emf, loop B has no induced emf, and loop C has clockwise emf.
E) loop A has counterclockwise emf, loop B clockwise emf, and loop C has clockwise emf.
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41
Suppose that you wish to construct a simple AC generator with an output of 12. V maximum when rotated at 60. Hz. A magnetic field of 0.050 T is available. If the area of the rotating coil is 100. cm2, how many turns are needed?
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42
A transformer with 120. turns in its secondary supplies 12. volts at 220. ma to a toy train. The primary is connected across a 120. V wall outlet.
(a) How many turns are in the primary?
(b) What is the primary current?
(c) What power is delivered by the wall outlet?
(a) How many turns are in the primary?
(b) What is the primary current?
(c) What power is delivered by the wall outlet?
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43
The windings of a DC motor have a resistance of 6.0 Ω. The motor operates
on 120. V AC, and when running at full speed it generates a back emf of 105. V.
(a) What is the starting current of the motor?
(b) What current does the motor draw when operating at full speed?
on 120. V AC, and when running at full speed it generates a back emf of 105. V.
(a) What is the starting current of the motor?
(b) What current does the motor draw when operating at full speed?
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44
A 60. Hz AC generator produces a maximum emf of 170. V. What is the value of the emf 0.025 s after it has reached its maximum value?
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45
A 80. volt DC motor draws 4.0 A at its operating speed of 1500. rpm with an
armature resistance of 4.0 Ω.
(a) What is the starting current?
(b) What is the back emf when running normally?
(c) What series resistance could be added to limit the starting current to 10. A?
armature resistance of 4.0 Ω.
(a) What is the starting current?
(b) What is the back emf when running normally?
(c) What series resistance could be added to limit the starting current to 10. A?
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46
A transformer has a turns ratio of 10. The primary voltage and current are 120. volts and 20. Amperes.
(a) What is the primary impedance (ratio of primary voltage to current)?
(b) What is the secondary impedance?
(a) What is the primary impedance (ratio of primary voltage to current)?
(b) What is the secondary impedance?
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47
FIGURE 23-5
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field whose strength is 0.40 T, as shown in Figure 23-5. The length of the loop L is 0.16 m and its width w is 0.04 m. What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field?
A) -2.6 × 10-3 T∙m2
B) +2.6 × 10-3 T∙m2
C) 0 T∙m2
D) -1.3 × 10-3 T∙m2
E) 1.3 × 10-3 T∙m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field whose strength is 0.40 T, as shown in Figure 23-5. The length of the loop L is 0.16 m and its width w is 0.04 m. What is the magnetic flux through the loop when the plane of the loop is parallel to the magnetic field?
A) -2.6 × 10-3 T∙m2
B) +2.6 × 10-3 T∙m2
C) 0 T∙m2
D) -1.3 × 10-3 T∙m2
E) 1.3 × 10-3 T∙m2
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48
A metal airplane flies horizontally at 200. m/s where the Earth's magnetic field
is vertical and is 45.0 μT. If the wingspan is 25.0 meters:
(a) what emf is induced across the wings?
(b) what wingspan would produce 1.0 volt emf?
(c) The plane reverses direction. Does the polarity of the wingtip emf change, i.e., if the left wing was positive, does it now become negative?
is vertical and is 45.0 μT. If the wingspan is 25.0 meters:
(a) what emf is induced across the wings?
(b) what wingspan would produce 1.0 volt emf?
(c) The plane reverses direction. Does the polarity of the wingtip emf change, i.e., if the left wing was positive, does it now become negative?
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49
A coil of 40. turns and cross-sectional area 12. cm2 is oriented perpendicular to a magnetic field, which varies from zero to 1.2 T in 0.02 s. What emf is induced in the coil?
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50
A coil of 160 turns and area 0.20 m2 is placed with its axis parallel to a magnetic field of 0.40 T. The magnetic field changes from 0.40 T in the x-direction to 0.40 T in the negative x-direction in 2.0 s. If the resistance of the coil is 16 Ω, at what rate is power generated in the coil?
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51
An ideal transformer steps down 120. volts to 12. volts and the 2630. turn secondary supplies 12. Amperes.
(a) Determine the current in the primary.
(b) Determine the turns ratio.
(c) What is the ratio of output power to input power?
(a) Determine the current in the primary.
(b) Determine the turns ratio.
(c) What is the ratio of output power to input power?
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52
FIGURE 23-5
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field with a strength of 0.40 T as shown in Figure 23-5. 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 × 10-3 T∙ m2
C) 0.80 T∙ m2
D) 2.6 × 10-3 T∙ m2
E) 0 T∙ m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field with a strength of 0.40 T as shown in Figure 23-5. 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 × 10-3 T∙ m2
C) 0.80 T∙ m2
D) 2.6 × 10-3 T∙ m2
E) 0 T∙ m2
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53
An ideal transformer has 60. turns on its primary coil and 300. turns on its secondary coil. If 120. V at 2.0 A is applied to the primary, what voltage and current are present in the secondary?
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54
The starting current in a DC motor is 20. A, but it normally operates on 110. volts with a back EMF of 90. volts.
(a) What is the resistance in the windings?
(b) What is the current at normal load?
(a) What is the resistance in the windings?
(b) What is the current at normal load?
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55
An AC generator rotating at 60. Hertz in a 300. Gauss field has 1000. turns and produces an rms voltage of 150. volts and an rms current of 70. Amperes.
(a) What is the peak current?
(b) What is the area of each turn in the coil?
(a) What is the peak current?
(b) What is the area of each turn in the coil?
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56
A power transmission line 50. km long has a total resistance of 0.60 Ω. A generator produces 100. V at 70. A. In order to reduce energy loss due to heating of the transmission line, the voltage is stepped up with a transformer with a turns ratio of 100:
1.
(a) What percentage of the original energy is lost when the transformer is used?
(b) What percentage of the original energy would be lost if the transformer were not used?
1.
(a) What percentage of the original energy is lost when the transformer is used?
(b) What percentage of the original energy would be lost if the transformer were not used?
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57
A circular coil of diameter 20. cm, with 16. turns is in a 0.13 Tesla field.
(a) Find the total flux through the coil when the field is perpendicular to the coil plane.
(b) If the coil is rotated in 10. ms so its plane is parallel to the field, find the average induced emf.
(a) Find the total flux through the coil when the field is perpendicular to the coil plane.
(b) If the coil is rotated in 10. ms so its plane is parallel to the field, find the average induced emf.
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58
A step-down transformer is needed to reduce a primary voltage of 120. V AC to
6.0 V AC. What turns ratio is required?
6.0 V AC. What turns ratio is required?
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59
A 90.% efficient transformer supplies 3.0 Amperes at 6.0 volts. If the input voltage is 120. v, what is the input current?
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60
An eagle, with a wingspread of 2.0 m, flies due North at 8.0 m/s in a region where the vertical component of the earth's magnetic field is 0.2 × 10-4 T. What emf would be developed between the eagle's wing tips?
(It has been speculated that this phenomenon could play a role in the navigation of birds, but the effect is too small, in all likelihood.)
(It has been speculated that this phenomenon could play a role in the navigation of birds, but the effect is too small, in all likelihood.)
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61
FIGURE 23-6
A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10-3 m2/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
A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10-3 m2/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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62
FIGURE 23-7
A bar magnet with its north pole pointing toward a coil of wire with a cross-sectional area of 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-7(b). If the rate of change in the strength of the magnetic field caused by the motion of the bar magnet is 0.040 T/s, what is the direction of the induced emf in the coil of wire (when looking at the end of the coil where the N pole is coming toward you)?
A) counterclockwise
B) clockwise
C) No emf is induced.
A bar magnet with its north pole pointing toward a coil of wire with a cross-sectional area of 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-7(b). If the rate of change in the strength of the magnetic field caused by the motion of the bar magnet is 0.040 T/s, what is the direction of the induced emf in the coil of wire (when looking at the end of the coil where the N pole is coming toward you)?
A) counterclockwise
B) clockwise
C) No emf is induced.
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63
FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the shaded face of the cube?
A) 4.0 × 10-1 T∙m2
B) 4.0 × 10-2 T∙m2
C) 4.0 × 10-3 T∙m2
D) 4.0 × 10-4 T∙m2
E) 0 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the shaded face of the cube?
A) 4.0 × 10-1 T∙m2
B) 4.0 × 10-2 T∙m2
C) 4.0 × 10-3 T∙m2
D) 4.0 × 10-4 T∙m2
E) 0 T∙m2
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64
A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop decreases at a rate of 3.0 × 10-3 m2/s, what is the induced emf in the loop?
A) 1.7 mV
B) 4.3 mV
C) 5.5 mV
D) 0 mV
E) 1.5 mV
A) 1.7 mV
B) 4.3 mV
C) 5.5 mV
D) 0 mV
E) 1.5 mV
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65
FIGURE 23-8
A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?
A) 7.2 V
B) 5.4 V
C) 9.2 V
D) 12 V
E) 0 V
A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?
A) 7.2 V
B) 5.4 V
C) 9.2 V
D) 12 V
E) 0 V
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66
FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the face of the cube along the y-z plane at x = 0?
A) 4.0 × 10-2 T∙m2
B) -4.0 × 10-3 T∙m2
C) -4.0 × 10-2 T∙m2
D) 4.0 × 10-3 T∙m2
E) 0 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field with a strength of 0.40 T is applied along the +x-axis. What is the magnetic flux through the face of the cube along the y-z plane at x = 0?
A) 4.0 × 10-2 T∙m2
B) -4.0 × 10-3 T∙m2
C) -4.0 × 10-2 T∙m2
D) 4.0 × 10-3 T∙m2
E) 0 T∙m2
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67
FIGURE 23-5
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field of strength 0.40 T as shown in Figure 23-5. 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) -1.3 × 10-3 T∙m2
B) 1.3 × 10-3 T∙m2
C) 0 T∙m2
D) -2.6 × 10-3 T∙m2
E) 2.6 × 10-3 T∙m2
A rectangular loop of wire carrying a current of 2.0 A that can rotate is placed in a magnetic field of strength 0.40 T as shown in Figure 23-5. 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) -1.3 × 10-3 T∙m2
B) 1.3 × 10-3 T∙m2
C) 0 T∙m2
D) -2.6 × 10-3 T∙m2
E) 2.6 × 10-3 T∙m2
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68
FIGURE 23-8
A constant magnetic field is applied perpendicular to the plane of a square, single-turn coil with each side equal to 15 cm. If the area of the coil decreases at a rate of 0.20 m2/s, an emf of 20 mV is induced in that coil. What is the strength of the magnetic field applied to the coil?
A) 0.10 T
B) 0.20 T
C) 0.30 T
D) 0.40 T
E) 0.50 T
A constant magnetic field is applied perpendicular to the plane of a square, single-turn coil with each side equal to 15 cm. If the area of the coil decreases at a rate of 0.20 m2/s, an emf of 20 mV is induced in that coil. What is the strength of the magnetic field applied to the coil?
A) 0.10 T
B) 0.20 T
C) 0.30 T
D) 0.40 T
E) 0.50 T
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69
FIGURE 23-8
A single-turn plane loop of wire with a cross-sectional area 200 cm2 is perpendicular to a magnetic field that increases uniformly from 0.200 T to 2.800 T in 2.20 seconds. What is the magnitude of the induced current if the resistance of the coil is 8.00 Ω?
A) 2.95 A
B) 3.18 A
C) 0 A
D) 3.18 mA
E) 2.95 mA
A single-turn plane loop of wire with a cross-sectional area 200 cm2 is perpendicular to a magnetic field that increases uniformly from 0.200 T to 2.800 T in 2.20 seconds. What is the magnitude of the induced current if the resistance of the coil is 8.00 Ω?
A) 2.95 A
B) 3.18 A
C) 0 A
D) 3.18 mA
E) 2.95 mA
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70
FIGURE 23-8
A bar magnet with its south pole pointing toward a loop of wire of cross-sectional area 0.020 m2 and total number of turns equal to six is stationary near the loop of wire shown in Figure 23-8(a). What is the direction of the induced emf in that loop of wire (when looking at the end of the coil where the S pole is coming toward you)?
A) clockwise
B) counterclockwise
C) There is no emf induced.
A bar magnet with its south pole pointing toward a loop of wire of cross-sectional area 0.020 m2 and total number of turns equal to six is stationary near the loop of wire shown in Figure 23-8(a). What is the direction of the induced emf in that loop of wire (when looking at the end of the coil where the S pole is coming toward you)?
A) clockwise
B) counterclockwise
C) There is no emf induced.
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71
The area of a rectangular loop of wire is 3.6 × 10-3 m2. The loop is placed in a magnetic field that changes 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 × 10-3 V
B) 2.7 × 10-3 V
C) 0 V
D) 1.8 × 10-3 V
E) 3.0 × 10-3 V
A) 2.8 × 10-3 V
B) 2.7 × 10-3 V
C) 0 V
D) 1.8 × 10-3 V
E) 3.0 × 10-3 V
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72
FIGURE 23-10
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance of 8.0 Ω as shown in Figure 23-10. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied out of the paper. An applied force moves the rod to the left with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 75 mA clockwise
B) 75 mA counterclockwise
C) 17 mA counterclockwise
D) 17 mA clockwise
E) 52 mA clockwise
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance of 8.0 Ω as shown in Figure 23-10. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied out of the paper. An applied force moves the rod to the left with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 75 mA clockwise
B) 75 mA counterclockwise
C) 17 mA counterclockwise
D) 17 mA clockwise
E) 52 mA clockwise
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73
A constant magnetic field of 0.50 T is applied to a rectangular loop of area 3.0 × 10-3 m2. If the area of this loop changes 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 × 10-2 V
B) 0 V
C) 7.5 × 10-2 V
D) 4.4 × 10-4 V
E) 9.0 × 10-2 V
A) 1.6 × 10-2 V
B) 0 V
C) 7.5 × 10-2 V
D) 4.4 × 10-4 V
E) 9.0 × 10-2 V
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74
FIGURE 23-8
A bar magnet with its south pole pointing toward a coil of wire of cross-sectional area 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-8(b). If the rate of change in the strength of the magnetic field caused by 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 bar magnet with its south pole pointing toward a coil of wire of cross-sectional area 0.020 m2 and seven turns is thrust into the coil as shown in Figure 23-8(b). If the rate of change in the strength of the magnetic field caused by 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
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75
FIGURE 23-9
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ω as shown in Figure 23-9. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s. What is the magnitude of the induced emf in the wire?
A) 0.2 V
B) 0.3 V
C) 0.4 V
D) 0.5 V
E) 0.6 V
A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ω as shown in Figure 23-9. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s. What is the magnitude of the induced emf in the wire?
A) 0.2 V
B) 0.3 V
C) 0.4 V
D) 0.5 V
E) 0.6 V
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76
A rectangular coil with dimensions of 8.0 cm × 10 cm is dropped from a zero magnetic field position to a 1.4 T magnetic field in 0.10 s. The coil has 60 turns and is perpendicular to the magnetic field. What is induced emf in the coil as a result of this?
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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77
A conducting loop of wire has an area of 150 cm2 and a resistance of 25.0 Ω. There is a magnetic field of 100 T perpendicular to the loop. At what rate must this field be reduced to induce a current of 0.100 A in the loop?
A) 167 T/s
B) 60.0 T/s
C) 5.58 T/s
D) 0.354 T/s
E) 120 T/s
A) 167 T/s
B) 60.0 T/s
C) 5.58 T/s
D) 0.354 T/s
E) 120 T/s
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78
FIGURE 23-9
A conducting rod with a length of 25 cm is placed on a U-shaped metal wire that has a resistance R of 8.0 Ω as shown in Figure 23-9. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied perpendicular into the paper. An applied force moves the rod to the right with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 17 mA clockwise
B) 17 mA counterclockwise
C) 75 mA counterclockwise
D) 75 mA clockwise
E) 52 mA clockwise
A conducting rod with a length of 25 cm is placed on a U-shaped metal wire that has a resistance R of 8.0 Ω as shown in Figure 23-9. The wire and the rod are placed in the plane of the paper. A constant magnetic field of strength 0.40 T is applied perpendicular into the paper. An applied force moves the rod to the right with a constant speed of 6.0 m/s. What is the magnitude and direction of the induced current in the wire?
A) 17 mA clockwise
B) 17 mA counterclockwise
C) 75 mA counterclockwise
D) 75 mA clockwise
E) 52 mA clockwise
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79
FIGURE 23-6
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field of strength 0.40 T is applied along the +x-axis. What is the total magnetic flux through the six faces of the cube?
A) 0 T∙m2
B) -4.0 × 10-3 T∙m2
C) +4.0 × 10-2 T∙m2
D) -4.0 × 10-2 T∙m2
E) 4.0 × 10-3 T∙m2
A cube whose edges are 0.10 m long has one corner at the origin of an xyz-coordinate system as shown in Figure 23-6. A magnetic field of strength 0.40 T is applied along the +x-axis. What is the total magnetic flux through the six faces of the cube?
A) 0 T∙m2
B) -4.0 × 10-3 T∙m2
C) +4.0 × 10-2 T∙m2
D) -4.0 × 10-2 T∙m2
E) 4.0 × 10-3 T∙m2
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80
FIGURE 23-7
A bar magnet is placed with its north pole pointing toward a coil of wire that has a cross-sectional area of 0.02 m2 and 6 turns, as shown in Figure 23-7(a). What is the magnitude of the induced emf in the coil of wire?
A) 0.04 V
B) 0.03 V
C) 0.01 V
D) 0.02 V
E) 0 V
A bar magnet is placed with its north pole pointing toward a coil of wire that has a cross-sectional area of 0.02 m2 and 6 turns, as shown in Figure 23-7(a). What is the magnitude of the induced emf in the coil of wire?
A) 0.04 V
B) 0.03 V
C) 0.01 V
D) 0.02 V
E) 0 V
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