set 4 MCQ Questions & Answers Detailed Explanation

Question : 1

A mobile phone charger is

a) A step up transformer

b) An inverter

c) A UPS

d) A step down transformer

Question : 2

Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to (E_g )_C , (E_g )_Si and (E_g )_Ge. Which of the following statements is true?

a) (E_g )_C < (E_g )_Ge < (E_g )_Si

b) (E_g )_C > (E_g )_Si > (E_g )_Ge

c) (E_g )_Si < (E_g )_Ge < (E_g )_C

d) (E_g )_C = (E_g )_Si = (E_g )_Ge

Question : 3

An oscillator is nothing but an amplifer with

a) negative feedback

b) large gain

c) positive feedback

d) no feedback

Question : 4

An electric bulb is connected to 220 V generator. The current is 0.5A. The power of the bulb is

a) 440 W

b) 110 W

c) 110 V

d) 220 W

Question : 5

In electric apparatus ‘Earth’ is used

a) For safety

b) To reduce the expenditure

c) Because the apparatus used 3-phase

d) In the form of fuse

Question : 6

In the figure shown below, $L_1$ and $L_2$ are two lenses and are kept along the same axis. A parallel beam of light falling on $L_1$ leaves $L_2$ as a parallel beam: Consider the following statements.

1. Both L1 and L2 can be convex lenses.
2. The distance between the two lenses can be equal to sum of their focal lengths.

a) Both 1 and 2

b) Only 1

c) Only 2

d) Neither 1 nor 2