Model Paper 3 — Physics STD 12 Science — Question

Least doped region in a transistor

(a) Either emitter or collector

(b) Base

(c) Emitter

(d) Collector

A solid conducting sphere having a charge Q is surrounded by an uncharged concentric conducting hollow spherical shell. Let the potential difference between the surface of the solid sphere and that of the outer surface of the hollow shell be V.  If the shell is now given a charge of –3Q, the new potential difference between the same two surfaces is

(a) V

(b) 2V

(c) 4V

(d) – 2V

If you are provided three resistances 2 W, 3 W and 6 W. How will you connect them so as to obtain the equivalent resistance of 4 W

(a)

(b)

(c)

(d) None of these

On cutting a solenoid in half, the field lines remain ...A... emerging from one face of the solenoid and entering into the other face.
Here, A refers to.

In intrinsic semiconductor at room temperature, number of electrons and holes are

(a) Unequal

(b) Equal

(c) Infinite

(d) Zero

The wrong statement about electric lines of force is

(a) These originate from positive charge and end on negative charge

(b) They do not intersect each other at a point

(c) They have the same form for a point charge and a sphere

(d) They have physical existence

When a glass rod is rubbed with silk, it

(a) Gains electrons from silk	(b) Gives electrons to silk
(c) Gains protons from silk	(d) Gives protons to silk

The essential distinction between X-rays and  γ - rays is that

(a) γ-  rays have smaller wavelength than X-rays

(b) γ - rays emanate from nucleus while X-rays emanate from outer part of the atom

(c) γ- rays have greater ionizing power than X-rays

(d) γ- rays are more penetrating than X-rays

The refractive index of water is 1.33. What will be the speed of light in water

(a) 3

(b) 2.25

(c) 4

(d) 1.33