Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

In NPN transistor the collector current is 10 mA. If 90% of electrons emitted reach the collector, then

(a) Emitter current will be 9 mA	(b) Emitter current will be 11.1 mA
(c) Base current will be 0.1 mA	(d) Base current will be 0.01 mA

Let V and H be the vertical and horizontal components of earth's magnetic field at any point on earth. Near the north pole

(a) V >> H

(b) V << H

(c) V = H

(d) V = H = 0

Two concentric coplanar circular loops of radii  and  carry currents of respectively  and  in opposite directions (one clockwise and the other anticlockwise.) The magnetic induction at the centre of the loops is half that due to  alone at the centre. If .  the value of   is

(a) 2

(b) 1/2

(c) 1/4

(d) 1

A 100% efficient transformer has 100 turns in the primary and 25 turns in its secondary coil. If the current in the secondary coil is 4 amp, then the current in the primary coil is

(a) 1 amp

(b) 4 amp

(c) 8 amp

(d) 16 amp

Identify the quantity which changes when a charged particle moves through a magnetic field?

Electric potential is given by T, hen electric force acting on 2C  point charge placed on origin will be

(a) 2N

(b) 6N

(c) 8N

(d) 20 N

The refractive index of a piece of transparent quartz is the greatest for

(a) Red light

(b) Violet light

(c) Green light

(d) Yellow light

A person sitting firmly over a rotating stool has his arms stretched. If he folds his arms, his angular momentum about the axis of rotation:

1. Increases.
2. Decreases.
3. Remains unchanged.
4. Doubles.

The graph which represents the relation between the total resistance R of a multi range moving coil voltmeter and its full scale deflection V is

(a) (i)

(b) (ii)

(c) (iii)

(d) (iv)

If current flowing through shell of previous objective is equal to i, then energy density at a point distance 2R from axis of the shell varies according to the graph

(a)

(b)

(c)

(d)