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Basic Electrical MCQs – General Science MCQs – 6

The class C insulation can withstand
(A) 180 °C
(B) 150 °C
(C) 200 °C
(D) 105 °C
Answer: Option A

The untreated paper falls in the following class of insulation
(A) A
(B) B
(C) E
(D) O
Answer: Option D

Mica tape falls under the following class of insulation
(A) A
(B) B
(C) E
(D) H
Answer: Option B

The material used for fuse must have
(A) Low melting point and low specific resistance
(B) Low melting point and high specific resistance
(C) High melting point and low specific resistance
(D) Low melting point with any specific resistance
Answer: Option B

The Buchhloz relay is used to protect the
(A) Alternators against all internal faults
(B) Oil immersed transformers against all internal faults
(C) Synchronous motor against all internal faults
(D) Transmission lines against all short-circuit faults
Answer: Option B

The earthing transformer is used
(A) To avoid the harmonics in the transformer
(B) To provide artificial neutral earthing where the neutral points of the three phase system are not accessible
(C) To improve the current capacity of the neutral wire
(D) To improve efficiency
Answer: Option B
The voltage regulation of a transformer is poor at
(A) Unity power factor
(B) Zero power factor
(C) Leading power factor
(D) Lagging power factor
Answer: Option D

The copper losses in a transformer at half load compared to those at full load will be
(A) Same
(B) Half
(C) One-fourth
(D) 2 times
Answer: Option C

It is essential that transformer oil should have no traces of moisture. The reason is that
(A) Density of oil increases with reduces heat dissipation
(B) Moisture will reduce the dielectric strength of the oil and hence insulation is weakened
(C) Moisture will reduce the lubricating property of the oil
(D) Moisture will develop rust
Answer: Option B

Which of the following electrical machines has the highest efficiency?
(A) D.C shunt motor
(B) Transformer
(C) Induction motor
(D) Synchronous motor
Answer: Option B