Physics - Study Mode

[#391] Alternating current is converted into direct current by a
Correct Answer

(D) Rectifier

Explanation

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.

[#392] Speed regulation of synchronous motor is
Correct Answer

(C) Zero

Explanation

Solution: Speed regulation of synchronous motor is zero.

[#393] 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
Correct Answer

(C) 7C

Explanation

Solution: The value of the capacitance will become 7C.

[#394] 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?
Correct Answer

(D) C1 = C2

Explanation

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.

[#395] Which compressor is usually used in AC?
Correct Answer

(C) Reciprocating

Explanation

Solution: The reciprocating compressor is the most popular type of AC compressor.