Canadian Basic pool, section 5-11

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Subelement 5

Basic Electronics and Theory

Section 5-11

introduction to magnetics, transformers

5-11-01

If no load is attached to the secondary winding of a transformer, what is current in the primary winding called?

Correct Answer
A.
Magnetizing current
B.
Direct current
C.
Excitation current
D.
Stabilizing current

5-11-01

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5-11-02

A transformer operates a 6.3 volt 2 ampere light bulb from its secondary winding. The power consumed by the primary winding is approximately:

Correct Answer
A.
13 watts
B.
6 watts
C.
8 watts
D.
3 watts

5-11-02

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5-11-03

A transformer has a 240 volt primary that draws a current of 250 mA from the mains supply. Assuming no losses, what current would be available from a 12 volt secondary?

A.
215 amperes
B.
25 amperes
C.
50 amperes
Correct Answer
D.
5 amperes

5-11-03

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5-11-04

In a mains power transformer, the primary winding has 250 turns, and the secondary has 500. If the input voltage is 110 volts, the likely secondary voltage is:

A.
440 V
Correct Answer
B.
220 V
C.
560 V
D.
24 V

5-11-04

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5-11-05

The strength of the magnetic field around a conductor in air is:

A.
inversely proportional to the diameter of the conductor
B.
directly proportional to the diameter of the conductor
Correct Answer
C.
directly proportional to the current in the conductor
D.
inversely proportional to the voltage on the conductor

5-11-05

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5-11-06

Maximum induced voltage in a coil occurs when:

Correct Answer
A.
current is going through its greatest rate of change
B.
the current through the coil is of a DC nature
C.
current is going through its least rate of change
D.
the magnetic field around the coil is not changing

5-11-06

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5-11-07

The voltage induced in a conductor moving in a magnetic field is at a maximum when the movement is:

A.
made in a counterclockwise direction
B.
parallel to the lines of force
Correct Answer
C.
perpendicular to the lines of force
D.
made in a clockwise direction

5-11-07

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5-11-08

A 100% efficient transformer has a turns ratio of 1/5. If the secondary current is 50 mA, the primary current is:

A.
2 500 mA
B.
0.01 A
Correct Answer
C.
0.25 A
D.
0.25 mA

5-11-08

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5-11-09

A force of repulsion exists between two _______ magnetic poles.

A.
unlike
B.
positive
C.
negative
Correct Answer
D.
like

5-11-09

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5-11-10

A permanent magnet would most likely be made from:

A.
copper
B.
aluminum
C.
brass
Correct Answer
D.
steel

5-11-10

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5-11-11

The fact that energy transfer from primary to secondary windings in a power transformer is not perfect is indicated by:

A.
electrostatic shielding
B.
large secondary currents
Correct Answer
C.
warm iron laminations
D.
high primary voltages

5-11-11

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