set 5 MCQ Questions & Answers Detailed Explanation

Question : 1

The Donor level in a semiconductor is placed

a) in the forbidden energy gap close to the upper edge of the valence band

b) in the conduction band close to the lower edge to the conduction band

c) half-way in the forbidden energy gap

d) in the forbidden energy gap close to the lower edge of the conduction band

Question : 2

Consider the following statements. An ordinary light bulb has a rather short life because the

1. Filament wire is not uniform.
2. Bulb cannot be evacuated completely.
3. Wires supporting the filament melt at high temperatures.

a) 1 and 3

b) 1 and 3

c) 2 and 3

d) 1, 2 and 3

Question : 3

Graphene is frequently in news recently. What is its importance?

1. It is a two-dimensional material and has good electrical conductivity.
2. It is one of the thinnest but strongest materials tested so far.
3. It is entirely made of silicon and has high optical transparency.
4. It can be used as ‘conducting electrodes’ required for touch screens, LCDs and organic LEDs.

a) 1, 2 and 4 only

b) 1 and 2 only

c) 3 and 4 only

d) 1, 2, 3 and 4

Question : 4

Domestic electrical wiring is basically a

a) Combination of series and parallel connections

b) Series connection

c) Parallel connection

d) Series connection within each room and parallel connective elsewhere

Question : 5

Electric motors operating at low voltages tend to burn out because

a) They draw heat proportional to $v^2$

b) They draw more current which is inversely proportional to the voltage

c) They draw more current which is inversely proportional to the square root of the voltage

d) Low voltage sets in electrical discharge

Question : 6

Consider the following statements regarding a motor car battery:

1. The voltage is usually 12 V.
2. Electrolyte used is hydrochloric acid.
3. Electrodes are lead and copper.
4. Capacity is expressed in ampere-hour.

a) 3 and 4

b) 1 and 2

c) 2 and 3

d) 1 and 4