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

A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be

(a) 1 mA

(b) 2 mA

(c) 4 mA

(d) None of these

For a triode, at   volt, the following observations were taken, .  The value of plate resistance will be

(a) 25 kW

(b) 20.8 kW

(c) 12.5 kW

(d) 100 kW

Hubble's law is related with

(a) Comet

(b) Speed of galaxy

(c) Black hole

(d) Planetary motion

In order to coincide the parabolas formed by singly ionised ions in one spectrograph and doubly ionized ions in the other Thomson’s mass spectrograph, the electric fields and magnetic fields are kept in the ratios 1 : 2 and 3 : 2 respectively. Then the ratio of masses of the ions is

(a) 3 : 4

(b) 1 : 3

(c) 9 : 4

(d) None of these

When a current of 1 ampere is passed through a conductor whose ends are maintained at temperature difference of 1 ℃, the amount of heat evolved or absorbed is called

(a) Peltier coefficient	(b) Thomson coefficient
(c) Thermoelectic power	(d) Thermo e.m.f.

A fish rising vertically up towards the surface of water with speed 3 ms^–1 observes a bird diving vertically down towards it with speed 9 ms^–1. The actual velocity of bird is

(a) 4.5 ms–1

(b) 5. ms–1

(c) 3.0 ms–1

(d) 3.4 ms–1

If the de-Broglie wavelengths for a proton and for a α - particle are equal, then the ratio of their velocities will be

(a) 4 : 1

(b) 2 : 1

(c) 1 : 2

(d) 1 : 4

To reduce the ripples in a rectifier circuit with capacitor filter: