B-005-11: Introduction to magnetics, transformers
B-005-11-01:
If no load is attached to the secondary winding of a transformer, what is current in the primary winding called?
Magnetizing current
Direct current
Excitation current
Stabilizing current
B-005-11-02:
A transformer operates a 6.3 volt 2 ampere light bulb from its secondary winding. The power consumed by the primary winding is approximately:
13 watts
6 watts
8 watts
3 watts
B-005-11-03:
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?
5 amperes
215 amperes
25 amperes
50 amperes
B-005-11-04:
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:
220 V
440 V
560 V
24 V
B-005-11-05:
The strength of the magnetic field around a conductor in air is:
directly proportional to the current in the conductor
inversely proportional to the diameter of the conductor
directly proportional to the diameter of the conductor
inversely proportional to the voltage on the conductor
B-005-11-06:
Maximum induced voltage in a coil occurs when:
current is going through its greatest rate of change
the current through the coil is of a DC nature
current is going through its least rate of change
the magnetic field around the coil is not changing
B-005-11-07:
The voltage induced in a conductor moving in a magnetic field is at a maximum when the movement is:
perpendicular to the lines of force
made in a counterclockwise direction
parallel to the lines of force
made in a clockwise direction
B-005-11-08:
A 100% efficient transformer has a turns ratio of 1/5. If the secondary current is 50 mA, the primary current is:
0.25 A
2 500 mA
0.01 A
0.25 mA
B-005-11-09:
A force of repulsion exists between two _________ magnetic poles.
like
unlike
positive
negative
B-005-11-10:
A permanent magnet would most likely be made from:
steel
copper
aluminum
brass
B-005-11-11:
The fact that energy transfer from primary to secondary windings in a power transformer is not perfect is indicated by:
warm iron laminations
electrostatic shielding
large secondary currents
high primary voltages
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