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

Question : 11

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) $I_{rms} = 1/√{2} I_O$

Question : 12 [NDA]

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 : 13

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 : 14

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

a) Toaster

b) Refrigerator

c) Heater

d) Press

Question : 15 [IAS (Pre) 1998]

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