Electronics — Physics STD 12 Science — Question

If luminous efficiency of a lamp is 2 lumen/watt and its luminous intensity is 42 candela, then power of the lamp is

(a) 62 W

(b) 76 W

(c) 138 W

(d) 264 W

The refractive indices of water and glass with respect to air are 1.2 and 1.5 respectively. The refractive index of glass with respect to water is

(a) 0.6

(b) 0.8

(c) 1.25

(d) 1.75

Consider two waves passing through the same string. Principle of superposition for displacement says that the net displacement of a particle on the string is sum of the displacements produced by the two waves individually. Suppose we state similar principles for the net velocity of the particle and the net kinetic energy of the particle. Such a principle will be valid for:

1. Both the velocity and the kinetic energy.
2. The velocity but not for the kinetic energy.
3. The kinetic energy but not for the velocity.
4. Neither the velocity nor the kinetic energy.

What is immaterial for an electric fuse wire

(a) Its specific resistance	(b) Its radius
(c) Its length	(d) Current flowing through it

The magnetic materials having negative magnetic susceptibility are:

A lens of focal power 0.5 D is

(a) A convex lens of focal length 0.5 m

(b) A concave lens of focal length 0.5 m

(c) A convex lens of focal length 2 m

(d) A concave lens of focal length 2 m

The emitter-base junction of a transistor is …… biased while the collector-base junction is ……. biased

(a) Reverse, forward

(b) Reverse, reverse

(c) Forward, forward

(d) Forward, reverse

The work done in moving a unit positive test charge over a closed path in an electric field is _____________.