Physics Principles and Problems 2009

Chapter 25: Electromagnetic Induction

Standardized Test Practice

1
A 0.15-m straight wire moves with a constant velocity of 7.0 m/s perpendicularly through a magnetic field. If the magnetic field has a strength of 0.40 T, what is the electromotive force?
A)0.42 V
B)2.6 V
C)2.8 V
D)19 V
2
A generator develops a maximum voltage of 155 V. A lightbulb that is placed in a series circuit with the generator draws an electric current of 0.60 A. What is the resistance of the bulb?
A)1.3 × 102 Ω
B)1.8 × 102 Ω
C)2.6 × 102 Ω
D)3.7 × 102 Ω
3
According to Lenz's law, the direction of an induced current in a conductor will be that which ________.
A)enhances the magnetic field change that initially induced the current
B)increases heat
C)increases voltage
D)opposes the magnetic field change that initially induced the current
4
The illustration shows a step-up transformer. The primary coil has Np = 250 turns and secondary coil has Ns = 4750 turns. If the input effective voltage is 83.0 V, what is the voltage in the secondary coil? (Assume that the transformer is 100% efficient.)

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A)1.12 × 103 V
B)1.58 × 103 V
C)2.07 × 103 V
D)2.23 × 103 V
5
The effective current in the secondary coil is 1.20 A, what is the effective current in the primary coil? (Assume the transformer is 100% efficient.)

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A)11.4 A
B)16.1 A
C)22.8 A
D)32.2 A
6
A 0.038-T magnetic field is directed horizontally. A 1.8-m straight wire that is perpendicular to the magnetic field moves in a direction 55° above horizontal. If an EMF of 0.21 V is induced in the wire, what is the wire's speed?
A)2.5 m/s
B)3.1 m/s
C)3.7 m/s
D)4.6 m/s
7
A 0.25-m straight wire moves at a speed of 4.4 m/s perpendicular to a magnetic field of strength 0.052 T. The wire is part of a circuit with a resistance of 0.48 Ω. What is the current through the wire?
A)0.027 A
B)0.12 A
C)0.36 A
D)0.44 A
8
A transformer consists of a 500-turn primary coil and a 2000-turn secondary coil. If the current in the primary coils is 3.0 A, what is the current in the secondary? (Assume that the transformer is 100% efficient.)
A)12 A
B)1.3 A
C)0.75 A
D)48A
9
The diagram shows a magnet and a coil of wire that is not carrying current. According to Lenz's law, what will happen if the north pole of the magnet is moved toward the left end of the coil?

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A)There will be an induced current in a clockwise direction (as viewed from the left end of the coil).
B)The left end of the coil will become a north pole.
C)Magnetic field lines will emerge from the right end of the coil.
D)A back-EMF will be induced.
10
A transformer is a device that ________.
  Need a Hint?
A)operates only on AC
B)operates only on DC
C)operates on either DC or AC
D)increases the power level of the circuit
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