Alternating Current  MCQs

MCQs of Alternating Current

Showing 61 to 70 out of 168 Questions
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61.
In an L-C-R series circuit, R = 50Ω L = 10 mH of an inductor and C = 20 μF, these components connected to A.C. source of 230 V, 50 Hz. The power in the circuit will be _____
(a) 98 W
(b) 89 W
(c) 980 W
(d) 98 mW
Answer:

Option (a)

62.
The ratio of primary and secondary turns in a transformer is 3 : 2, if 30V a.c. is fed to primary, voltage across secondary will be _____
(a) 15V
(b) 45V
(c) 90V
(d) 300V
Answer:

Option (b)

63.
A step-up transformer operates on a 230V line and supplies 2A to a load. The ratio of primary and secondary windings in 1 : 25, then the current in primary is _____
(a) 15A
(b) 25A
(c) 50A
(d) 12.5A
Answer:

Option (c)

64.
If number of turns in primary and secondary coils is increased to two times each, the mutual inductance _____
(a) becomes four times
(b) becomes two times
(c) becomes 14 times
(d) remains unchanged
Answer:

Option (a)

65.
A transformer is used to light 140 W, 24 V lamp from 240V A.C. mains. The current in the mains is 0.7 A. The efficiency of transformer is nearest to _____
(a) 90%
(b) 80%
(c) 70%
(d) 60%
Answer:

Option (b)

66.
In a noiseless transformer, an alternating current of 2A is flowing in primary coil. The number of turns in primary and secondary coil are 100 and 20 respectively the secondary current is _____
(a) 0.4 A
(b) 5 A
(c) 0.08 A
(d) 10 A
Answer:

Option (d)

67.
In an ideal transformer, the voltage is stepped down from 11 kV to 220 V. If the primary current be 100 A, the current in the secondary should be _____
(a) 5 kA
(b) 1 kA
(c) 0.5 kA
(d) 0.1 kA
Answer:

Option (a)

68.
If the coils of a transformer are made up of thick wire, then _____
(a) eddy currents loss will be more
(b) magnetic flux leakage is reduced
(c) joule's heating loss is increased
(d) joule's heating loss is reduced
Answer:

Option (d)

69.
Transformer are used in _____
(a) DC circuits only
(b) AC circuits only
(c) Integrated circuits
(d) All above these
Answer:

Option (b)

70.
In a step-down transformer _____ increases.
(a) current
(b) voltage
(c) power
(d) frequency
Answer:

Option (a)

Showing 61 to 70 out of 168 Questions
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