Practice Test: Question Set - 03
1. When both the inductance and resistance of a coil are doubled the value of
- (A) Time constant remains unchanged
- (B) Initial rate of rise of current is doubled
- (C) Final steady current is doubled
- (D) Time constant is halved
2. Hard steel is suitable for making permanent magnets because
- (A) It has good residual magnetism
- (B) Its hysteresis loop has large area
- (C) Its mechanical strength is high
- (D) Its mechanical strength is low
3. The relative permeability of a ferromagnetic material is
- (A) Less than one
- (B) More than one
- (C) More than 10
- (D) More than 100 or 1000
4. Relative permeability of vacuum is
- (A) 1
- (B) 1 H/m
- (C) 1/4JI
- (D) 4n × 10' H/m
5. Those materials are well suited for making permanent magnets which have ________ retentivity and ________ coercivity.
- (A) Low, high
- (B) High, high
- (C) High, low
- (D) Low, low
6. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit?
- (A) E.m.f.
- (B) Current
- (C) Current density
- (D) Conductivity
7. Permeability in a magnetic circuit corresponds to______ in an electric circuit.
- (A) Resistance
- (B) Resistivity
- (C) Conductivity
- (D) Conductance
8. Energy stored by a coil is doubled when its current is increased by percent.
- (A) 25
- (B) 50.14
- (C) 41.4
- (D) 100
9. A material for good magnetic memory should have
- (A) Low hysteresis loss
- (B) High permeability
- (C) Low retentivity
- (D) High retentivity
10. Laminated cores, in electrical machines, are used to reduce
- (A) Copper loss
- (B) Eddy current loss
- (C) Hysteresis loss
- (D) All of the above
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