set 8 MCQ Questions & Answers Detailed Explanation

Question : 1

Assertion (A):
Light Emitting Diode (LED) lamps offer longer service life as compared to Compact Fluorescent Lamps (CFL).
Reason (R):
Light Emitting Diodes (LED) lamps are more energy efficient as compared to the Compact Fluorescent Lamps (CFL).
Select the correct answer using the codes given below.
Code

a) (A) is true, but (R) is false

b) Both (A) and (R) are true and (R) is the correct explanation of (A)

c) Both (A) and (R) are true, but (R) is not the correct explanation of (A)

d) (A) is false, but (R) is true

Question : 2

To use a transistor as an amplifier

a) no bias voltage is required

b) both junctions are forward biased

c) The emitter base junction is forward biased and the base collector junction is reverse biased

d) both junctions are reverse biased

Question : 3

Two wires have their lengths, diameters and resistivities all in the ratio of 1 : 2. If the resistance of the thinner wire is 10 ohm, the resistance of the thicker wire is

a) 20 ohm

b) 5 ohm

c) 10 ohm

d) 40 ohm

Question : 4

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 : 5

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 : 6

In an a.c. circuit, the r.m.s. value of current, Irms is related to the peak current, I0 by the relation

a) $I_{rms} = π I_O$

b) $I_{rms} = {1/π}I_O$

c) $I_{rms} = √{2} I_O$

d) $I_{rms} = 1/√{2} I_O$