In a forward biased p-n junction diode, the potential barrier in the depletion region is of the form

If the forward voltage in a diode is increased, the width of the depletion region

• increases

• decreases

• fluctuates

• no change

Four metal conductors having different shape

1. a sphere
2. cylinder
3. pear
4. lightning conductor

are mounted on insulating stands and charged. The one which is best suited to retain the charges for a longer time is

• 1

• 2

• 3

• 4

The potential to which a conductor is raised, depends on

• the amount of charge

• geometry and size of the conductor

• Both (a) and (b)

• only on (a)

Identify the property which is not characteristic for a semiconductor ?

• At a very low temperatures, it behaves like a insulator

• At higher temperatures two types of charge carriers will cause conductivity

• The charge carriers are electrons and holes in the valence band at higher temperatures

• The semiconductor is electrically neutral

96.

Identify the operation performed by the circuit given below

• NOT

• AND

• OR

• NAND

In a transistor the collector current is always less than the emitter current because

• collector side is reverse biased and the emitter side is forward biased

• a few electrons are lost in the base and only remaining ones reach the collector

• collector being reverse biased, attracts less electrons

• collector side is forward biased and emitter side is reverse biased

To a germanium crystal equal number of aluminium and indium atoms are added. Then

• it remains an intrinsic semiconductor

• it becomes a n-type semiconductor

• it becomes a p-type semiconductor

• it becomes an insulator

Minority carriers in a p-type semiconductor are

• free electrons

• holes

• neither holes nor free electrons

• both holes and free electrons

In a reverse biased diode when the applied voltage changes by 1 V, the current is found to change by 0.5 µA. The reverse bias resistance of the diode is

• 2 × 10⁵ Ω

• 2 × 10⁶ Ω

• 200 Ω

• 2 Ω