electric current and magnetism - Category wise Question and Answer Practice Test with Solutions

Question : 11

When an n–p–n transistor is used as an amplifier then

a) holes flow from emitter to collector

b) electrons flow from collector to emitter

c) electrons flow from emitter to collector

d) electrons flow from battery to emitter

Question : 12 [NDA]

A coin in a beaker filled with water appears raised. This phenomenon occurs because of the property of

a) total internal reflection of light

b) reflection of light

c) refraction of light

d) interference of light

Question : 13 [IAS Prelim]

Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?

a) Moisture in the upper layers of atmosphere prevents them from reaching the surface of the Earth

b) The Earth’s magnetic field diverts them towards its poles

c) Ozone layer around the Earth reflects them back to outer space

d) None of the statements (a), (b) and (c) given above is correct

Question : 14 [NDA]

Magnetism of a bar magnet can be destroyed if it is

1. kept in the magnetic meridian.
2. placed in a direction opposite to that of the Earth's horizontal intensity.
3. heated to a temperature known as Curie temperature.

a) II and III only

b) I and III only

c) II only

d) I, II and III

Question : 15

In a common base amplifier the phase difference between the input signal voltage and the output voltage is

a) π/4

b) π/2

c) 0

d) π