Electric Charges and Fields — Physics STD 12 Science — Question

For the propagation of light wave, medium is required. This is according to:

Mark the correct statements about the friction between two bodies:

1. Static friction is always greater than the kinetic friction.
2. Coefficient of static friction is always greater than the coefficient of kinetic friction.
3. Limiting friction is always greater than the kinetic friction.
4. Limiting friction is never less than static friction.

Two identical metal plates show photoelectric effect by a light of wavelength   falls on plate A and   on plate B (. The maximum kinetic energy is

(a) 2

(b)

(c)

(d)

The average e.m.f. induced in a coil in which a current changes from 0 to 2 A in 0.05 s is 8 V. The self inductance of the coil is

(a) 0.1 H

(b) 0.2 H

(c) 0.4 H

(d) 0.8 H

Light energy emitted by stars is due to

(a) Breaking of nuclei	(b) Joining of nuclei
(c) Burning of nuclei	(d) Reflection of solar light

As shown in the figure, a magnet is moved with a fast speed towards a coil at rest. Due to this induced electromotive force, induced current and induced charge in the coil is E, I and Q  respectively. If the speed of the magnet is doubled, the incorrect statement is

(a) E increases

(b) I increases

(c) Q remains same

(d) Q increases

A coil of wire of a certain radius has 100 turns and a self-inductance of 15 mH. The self-inductance of a second similar coil of 500 turns will be:

A copper rod of length l is rotated about one end perpendicular to the magnetic field B with constant angular velocity ω. The induced e.m.f. between the two ends is

(a)

(b)

(c)

(d)

In P-N junction, the barrier potential offers resistance to

(a) Free electrons in N region and holes in P region

(b) Free electrons in P region and holes in N region

(c) Only free electrons in N region

(d) Only holes in P region