Question 1

Assertion (A): When a high reverse voltage is applied to a p-n junction the diode breaks down. Reason (R): High reverse voltage causes Avalanche effect.

Accepted Answer

Avalanche breakdown occurs at high reverse voltage.

Question 2

An LED has a rating of 2 V and 10 mA. It is used along with 6V battery. The range of series resistance is

Accepted Answer

R = = 400Ω. R must be at least 400Ω so that current in LED does not exceed 10 mA.

Question 3

Work function of oxide coated cathode is much lower than that of tungsten cathode.

Accepted Answer

Therefore emission current from oxide coated cathode is more.

Question 4

Assertion (A): A p-n junction has high resistance in reverse direction. Reason (R): When a reverse bias is applied to p-n junction, the width of depletion layer increases.

Accepted Answer

The increase in reverse resistance is due to widening of depletion layer.

Question 5

The minority carrier life time and diffusion constant in a semiconductor material are respectively 100 microsecond and 100 cm2/sec. The diffusion length is

Accepted Answer

Diffusion length = .

Question 6

As compared to an ordinary semiconductor diode, a Schottky diode

Accepted Answer

This is due to high electron concentration in metals.

Question 7

In a p type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be

Accepted Answer

Addition of acceptor atom brings Fermi level closer to valence band.

Question 8

The most commonly used semiconductor material is

Accepted Answer

Germanium is rarely used.

Question 9

Which of the following is true as regards photo emission?

Accepted Answer

As wavelength decreases, frequency increases and maximum velocity of electron increases.

Question 10

If aac for transistor is 0.98 then βac is equal to

Accepted Answer

.

Electronic Devices and Circuits Questions