Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

One magnet is moved towards a coil, first speedily and then slowly. Then amount of electric charge induced would be __________ .

A uniform sphere is placed on a smooth horizontal surface and a horizontal force F is applied on it at a distance h above the surface. The acceleration of the centre:

1. Is maximum when h = 0.
2. Is maximum when h = R.
3. Is maximum when h = 2R.
4. Is independent of h.

In a photoelectric experiment for 4000 Å incident radiation, the potential difference to stop the ejection is 2 V. If the incident light is changed to 3000 Å, then the potential required to stop the ejection of electrons will be

(a) 2 V

(b) Less than 2 V

(c) Zero

(d) Greater than 2 V

According to Bohr's theory, the expressions for the kinetic and potential energy of an electron revolving in an orbit is given respectively by

(a) +  and	(b) + and
(c)  and	(d)  +  and +

Two bulbs X and Y having same voltage rating and of power 40 watt and 60 watt respectively are connected in series across a potential difference of 300 volt, then

(a) X will glow brighter	(b) Resistance of Y is greater than X
(c) Heat produced in Y will be greater than X	(d) Voltage drop in X will be greater than Y

A satellite is orbiting the earth close to its surface. A particle is to be projected from the satellite to just escape from the earth. The escape speed from the earth is νe. Its speed with respect to the satellite:

1. Will be less than ν_e.
2. Will be more than ν_e.
3. Will be equal to ν_e.
4. Will depend on the direction of projection.

When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then

(a) The stopping potential will be 0.2 V	(b) The stopping potential will be 0.6 V
(c) The saturation current will be 6 mA	(d) The saturation current will be 18 mA

The critical angle of a medium with respect to air is 45°. The refractive index of medium is

(a) 1.41

(b) 1.2

(c) 1.5

(d) 2

Assertion   :  Electric appliances with metallic body have three connections, whereas an electric bulb has a two pin connection.

Reason       : Three pin connections reduce heating of connecting wires.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Ionization potential of hydrogen atom is 13.6 V.

Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be

(a) One

(b) Two

(c) Three

(d) Four