18
2-52. If the permeability of the core of a coil
decreases, what happens to the (a)
inductance and (b) true power in the
circuit?
1. (a) Increases
(b) increases
2. (a) Increases
(b) decreases
3. (a) Decreases
(b) increases
4. (a) Decreases
(b) decreases
2-53. If the current in an iron-core coil is
increased to a large value (from the
operating point) what happens to the
permeability of the core?
1. It increases
2. It decreases
3. It remains the same
4. It increases initially and then
decreases rapidly
2-54. If two coils are wound on a single iron
core, a change in current in one coil
(a) will or will not cause a change in
inductance and (b) will or will not cause
a change in current in the other coil.
1. (a) Will
(b) will
2. (a) Will
(b) will not
3. (a) Will not
(b) will
4. (a) Will not
(b) will not
Figure 2H.—Saturable-core reactor.
IN ANSWERING QUESTION 2-55, REFER
TO FIGURE 2H.
2-55. What portion of the schematic diagram
indicates a saturable core?
1. a
2. b
3. c
4. d
2-56. A magnetic amplifier should be operated
on what portion of the magnetization
curve?
1. The positive peak
2. The negative peak
3. The mid-point
4. The knee
2-57. A toroidal core is used in a saturable-core
reactor to counteract which of the
following effects?
1. Hysteresis
2. Copper loss
3. Both 1 and 2 above
4. The effect of load flux on control
flux
2-58. Why is a rectifier used in a magnetic
amplifier?
1. To decrease current
2. To eliminate hysteresis loss
3. To increase the power-handling
capability
4. To convert the magnetic amplifier
from an a.c. device to a d.c. device.
2-59. What can be used to set a magnetic
amplifier to the proper operating point
and leave the control winding free to
accept input signals?
1. A filter
2. A bias winding
3. A d.c. power source
4. A feedback network
2-60. A magnetic amplifier would not be used
in which of the following devices?
1. A servo system
2. A d.c. power supply
3. Temperature indicators
4. A wideband audio power amplifier
system
