Question 1

Metal detectors,like the ones used at airports,are activated by

Accepted Answer

A) electric fields. 
B) magnetic fields. 
C) electromagnetic induction. 
D) alternating current. 
A) electric fields. 
B) magnetic fields. 
C) electromagnetic induction. 
D) alternating current.

Question 2

Neon signs require about 12,000 volts to operate.If the circuit uses a 120-volt power source,the ratio of primary to secondary turns on the transformer should be

Accepted Answer

A) 1:100. 
B) 100:1. 
C) neither of these 
A) 1:100. 
B) 100:1. 
C) neither of these

Question 3

The metal detectors that people walk through at airports operate via

Accepted Answer

A) Ohm's law. 
B) Faraday's law. 
C) Coulomb's law. 
D) Newton's laws. 
E) civil laws. 
A) Ohm's law. 
B) Faraday's law. 
C) Coulomb's law. 
D) Newton's laws. 
E) civil laws.

Question 4

Transformers use ac so there will be the required

Accepted Answer

A) transfer of energy from coil to coil. 
B) voltage for transformation. 
C) change in magnetic field for operation. 
D) change in input current. 
E) magnetic field intensities. 
A) transfer of energy from coil to coil. 
B) voltage for transformation. 
C) change in magnetic field for operation. 
D) change in input current. 
E) magnetic field intensities.

Question 5

Use the following figure to answer the question:  
-A step-up transformer increases

Accepted Answer

A) power. 
B) energy. 
C) both power and energy. 
D) neither power or energy. 
A) power. 
B) energy. 
C) both power and energy. 
D) neither power or energy.

Question 6

Rapid change of a magnetic field induces

Accepted Answer

A) a magnetic field of greater magnitude. 
B) a magnetic field of the same magnitude. 
C) an electric field. 
A) a magnetic field of greater magnitude. 
B) a magnetic field of the same magnitude. 
C) an electric field.

Question 7

If a magnet is pushed into a coil,voltage is induced across the coil.If the same magnet is pushed into a coil with twice the number of loops

Accepted Answer

A) one half as much voltage is induced. 
B) the same voltage is induced. 
C) twice as much voltage is induced. 
D) four times as much voltage is induced. 
E) none of these 
A) one half as much voltage is induced. 
B) the same voltage is induced. 
C) twice as much voltage is induced. 
D) four times as much voltage is induced. 
E) none of these

Question 8

Compared to the primary voltage,the secondary voltage may be

Accepted Answer

A) larger. 
B) smaller. 
C) the same. 
D) the same or smaller,but not larger. 
E) larger,smaller,or the same. 
A) larger. 
B) smaller. 
C) the same. 
D) the same or smaller,but not larger. 
E) larger,smaller,or the same.

Question 9

If the primary of a transformer were connected to a dc power source,the transformer would have a voltage output

Accepted Answer

A) at a higher efficiency than with an ac source. 
B) the same. 
C) that is also dc. 
D) only while being connected or disconnected. 
E) none of these 
A) at a higher efficiency than with an ac source. 
B) the same. 
C) that is also dc. 
D) only while being connected or disconnected. 
E) none of these

Question 10

The major advantage of MHD generators over conventional generators is that MHD generators

Accepted Answer

A) do not use electromagnetic induction. 
B) do not require magnets. 
C) require no power input. 
D) all of these 
E) none of these 
A) do not use electromagnetic induction. 
B) do not require magnets. 
C) require no power input. 
D) all of these 
E) none of these

Question 11

Voltage can be induced in a wire by

Accepted Answer

A) moving the wire near a magnet. 
B) moving a magnet near the wire. 
C) changing the current in a nearby wire. 
D) Choices A,B,and C are all true. 
E) None of the above choices are true. 
A) moving the wire near a magnet. 
B) moving a magnet near the wire. 
C) changing the current in a nearby wire. 
D) Choices A,B,and C are all true. 
E) None of the above choices are true.

Question 12

A transformer actually transforms

Accepted Answer

A) voltage. 
B) magnetic field lines. 
C) generators into motors. 
D) non-safe forms of energy to safe forms of energy. 
E) All of the above choices are correct. 
A) voltage. 
B) magnetic field lines. 
C) generators into motors. 
D) non-safe forms of energy to safe forms of energy. 
E) All of the above choices are correct.

Question 13

A wire moving at right angles to a magnetic field has NO induced voltage

Accepted Answer

A) if it is made of copper. 
B) if it is moving slowly. 
C) if it is moving very fast. 
D) if the wire is covered with insulation. 
E) None of the above choices are correct. 
A) if it is made of copper. 
B) if it is moving slowly. 
C) if it is moving very fast. 
D) if the wire is covered with insulation. 
E) None of the above choices are correct.

Exam 25: Electromagnetic Induction

Metal detectors,like the ones used at airports,are activated by

Neon signs require about 12,000 volts to operate.If the circuit uses a 120-volt power source,the ratio of primary to secondary turns on the transformer should be

The metal detectors that people walk through at airports operate via

Transformers use ac so there will be the required

Use the following figure to answer the question: -A step-up transformer increases

Rapid change of a magnetic field induces

If a magnet is pushed into a coil,voltage is induced across the coil.If the same magnet is pushed into a coil with twice the number of loops

Compared to the primary voltage,the secondary voltage may be

If the primary of a transformer were connected to a dc power source,the transformer would have a voltage output

The major advantage of MHD generators over conventional generators is that MHD generators

Voltage can be induced in a wire by

A transformer actually transforms

A wire moving at right angles to a magnetic field has NO induced voltage

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