set 8 MCQ Questions & Answers Detailed Explanation

Question : 1

Two thin convex lenses of focal lengths 4 cm and 8 cm are separated by a distance of 4 cm in air. The combination will have the focal length

a) 12 cm

b) 4 cm

c) 8 cm

d) 32 cm

Question : 2

p-n junction is said to be forward biased, when

a) the positive pole of the battery is joined to the n-semiconductor and p-semiconductor

b) the positive pole of the battery is connected to n- semiconductor and p- semiconductor

c) the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor

d) a mechanical force is applied in the forward direction

Question : 3

Which is not a device based on the heating effect of electricity?

a) Toaster

b) Refrigerator

c) Heater

d) Press

Question : 4

From a power station, the power is transmitted at a very high voltage because –

a) it is cheaper to produce electricity at high voltage

b) electricity at high voltage is less dangerous

c) it is generated only at high voltage

d) there is less loss of energy in transmission at high voltage

Question : 5

To convert mechanical energy into electrical energy, one can use

a) AC dynamo

b) DC dynamo

c) motor

d) Both (a) & (b)

Question : 6

Transformers are used

a) in AC circuits only

b) in both DC and AC circuits

c) in DC circuits only

d) neither in DC nor in AC circuits