set 9 MCQ Questions & Answers Detailed Explanation

Question : 1

The current in the armature of a motor is reversed at every half cycle due to the action of a(n)

a) field coil

b) brush

c) armature

d) commutator

Question : 2

What gases are filled in fluorescent tube?

a) Mercury

b) Neon

c) Sodium

d) Mercury and neon

Question : 3

When a forward bias is applied to a p-n junction, it

a) reduces the majority carrier current to zero.

b) lowers the potential barrier.

c) raises the potential barrier.

d) None of these

Question : 4

Due to the earth's magnetic field, charged cosmic ray particles

a) can never reach the equator

b) require greater kinetic energy to reach the equator than the poles

c) require less kinetic energy to reach the equator than the poles

d) can never reach the poles

Question : 5

In the circuits shown below the ammeter A reads 4 amp. and the voltmeter V reads 20 volts. The value of the resistance R is

a) slightly less than 5 ohms

b) exactly 5 ohms

c) slightly more than 5 ohms

d) None of these

Question : 6

When n-type semiconductor is heated

a) number of holes increases while that of electrons decreases

b) number of electrons and holes remain same

c) number of electrons increases while that of holes decreases

d) number of electrons and holes increases equally