Electrical Measurements & Measuring Instruments Multiple Choice Questions on “Instrument Transformers”.
1. What is the current transformer?
a) transformer used with an A.C. ammeter
b) transformer used with an D.C. ammeter
c) transformer used with an A.C. voltmeter
d) transformer used with an D.C. voltmeter
Answer: a
Clarification: A transformer used to extend the range of an A.C. ammeter is known as a current transformer. A current transformer is also abbreviated as C.T.
2. What is the potential transformer?
a) transformer used with an D.C. ammeter
b) transformer used with an A.C. voltmeter
c) transformer used with an D.C. ammeter
d) transformer used with an A.C. voltmeter
Answer: b
Clarification: A transformer used to extend the range of an A.C. voltmeter is known as a potential transformer. A potential transformer is also abbreviated as P.T.
3. C.T. and P.T. are used for _________
a) measuring low current and voltages
b) measuring very low current and voltages
c) measuring high currentsand voltages
d) measuring intermediate currents and voltages
Answer: c
Clarification: C.T. is basically used for the measurement of high currents. A P.T. is usually used for the measurement of high voltages. They are used with A.C. ammeters and voltmeters in order to extend their range.
4. The primary winding of a C.T. has _________
a) a larger number of turns
b) no turns at all
c) intermediate number of turns
d) a few turns
Answer: d
Clarification: The primary winding of a C.T. has a very few number of turns. It is connected in series with the load circuit through which the primary current flows.
5. The secondary winding of a C.T. has _________
a) a large number of turns
b) a few turns
c) no turns at all
d) intermediate number of turns
Answer: a
Clarification: Secondary winding of a C.T. has a large number of turns. It is connected in series to an ammeter through which a small portion of the current flows through.
6. Turns ration for a C.T. is _________
a) n = Np ⁄ Ns
b) n = Ns ⁄ Np
c) n = 1 ⁄ Np
d) n = Ns
Answer: b
Clarification: The turns ratio for a C.T. is defined as the ratio of the number of turns in the secondary to the number of turns in the primary. It is given by the relation
n = Ns⁄Np
7. The primary winding of a P.T. has _________
a) intermediate number of turns
b) no turns at all
c) a larger number of turns
d) a few turns
Answer: c
Clarification: The primary winding of a P.T. has a very large number of turns. It is connected in parallel with the load whose voltage is to be measured.
8. The secondary winding of a P.T. has _________
a) a large number of turns
b) intermediate number of turns
c) no turns at all
d) a few turns
Answer: d
Clarification: Secondary winding of a P.T. has a few number of turns. A low range voltmeter is connected in parallel with the secondary winding.
9. Turns ration for a C.T. is _________
a) n = Np ⁄ Ns
b) n = Ns ⁄ Np
c) n = 1 ⁄ Np
d) n = Ns
Answer: a
Clarification: The turns ratio for a P.T. is defined as the ratio of the number of turns in the primary to the number of turns in the secondary. It is given by the relation
n = Np⁄Ns.
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