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Practice MCQ Questions and answers on Physics-GK

Learn and practice General Knowledge questions and answers on Physics with very easy and understandable explanations. GK questions are very helpful different type of competitive exams. Page-5 section-12

Each section contains 100 MCQs on Physics .
41
Which sources produce alternating current (AC)?
Discuss
Answer & Solution
Answer: Option B
Solution:
The sources are hydroelectric power plants, thermal power generators,nuclear power generators, AC generators.
42
Alternating current is converted into direct current by a
Discuss
Answer & Solution
Answer: Option D
Solution:
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification, since it "straightens" the direction of current.
43
Speed regulation of synchronous motor is
Discuss
Answer & Solution
Answer: Option C
Solution:
Speed regulation of synchronous motor is zero.
44
A parallel-plate capacitor,with air in between the plates, has capacitance C. Now the space between the two plates of the capacitor is filled with a dielectric of dielectric constant 7. Then the value of the capacitance will become
Discuss
Answer & Solution
Answer: Option C
Solution:
The value of the capacitance will become 7C.
45
A parallel-plate capacitor of capacitance C1 is made using two gold plates. Another parallel-plate capacitor of capacitance C2 is made using two aluminium plates with same plate separation, and all the four plates are of same area. If rg and ra are respectively the electrical resistivities of gold and aluminium, then which one of the following relations is correct?
Discuss
Answer & Solution
Answer: Option D
Solution:
C1= capacitance of gold plates
C2= capacitance of aluminium plates
rg= Gold’s resistivity
ra= Aluminium’s resistivity
As the capacitance depends on the shape, size & geometrical placing of the conductors & the medium between them, hence, the value of capacitance will be independent of resistivity. Therefore, C1= C2.
46
Which compressor is usually used in AC?
Discuss
Answer & Solution
Answer: Option C
Solution:
The reciprocating compressor is the most popular type of AC compressor.
47
The best material for the core of a transformer is
Discuss
Answer & Solution
Answer: Option D
Solution:
Soft iron provides the best material for the core of a transformer as its permeability (μ) is very high. Its hysteresis curve is of small area and its coercivity is very low.
48
A transformer works on the principle of
Discuss
Answer & Solution
Answer: Option B
Solution:
A transformer consists of two electrically isolated coils and operates on Faraday's principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.
49
Transformer is a device to convert
Discuss
Answer & Solution
Answer: Option C
Solution:
A transformer is an electrical device that transfers energy from one circuit to another by magnetic coupling with no moving parts. It converts high voltage AC into low voltage AC and vice-versa. It is based upon the principle of mutual induction. Transformers alone cannot convert AC to DC or DC to AC; besides, they cannot change the voltage or current of DC.
50
Atomic hydrogen has a life period of
Discuss
Answer & Solution
Answer: Option D
Solution:
Atomic hydrogen is unstable and it has life period of a fraction of a second.