modern and space physics, sources of energy - Category wise Question and Answer Practice Test with Solutions

Question : 16

Which of the following statements is/are correct ?

1. Pure Si doped with trivalent impurities gives a p-type semiconductor
2. Majority carriers in a n-type semiconductor are holes
3. Minority carriers in a p-type semiconductor are electrons
4. The resistance of intrinsic semiconductor decreases with increase of temperature

a) I, III and IV

b) I and IV

c) I only

d) II only

Question : 17

Match the List I and List II.

a) A – 4 ; B – 2 ; C – 3 ; D – 1

b) A – 2 ; B – 3 ; C – 4 ; D – 1

c) A – 3 ; B – 4 ; C – 1 ; D – 2

d) A – 2 ; B – 4 ; C – 1 ; D – 3

Question : 18

A moderator is used in nuclear reactors in order to

a) acceleerate the neutrons

b) increase the number of neutrons

c) slow down the speed of the nuetrons

d) decrease the number of neutrons

Question : 19 [CDS]

A perfect black body has the unique characteristic feature as

a) a good radiator only

b) a good absorber and a good radiator

c) a good absorber only

d) neither a radiator nor an absorber

Question : 20 [NDA]

Electromagnetic radiations are emitted by which of the following?

a) Only by bodies at temperature higher than their surroundings

b) Only by red-hot bodies

c) Only by radio and television transmitting antennas

d) By all bodies