electric current and magnetism - Category wise Question and Answer Practice Test with Solutions

electric current and magnetism PRACTICE TEST [9 - EXERCISES]

set 1

set 2

set 3

set 4

set 5

set 6

set 7

set 8

set 9

Question : 1 [IAS Prelim]

Fluorescent tubes are fitted with a choke. The choke coil :

a) reduces current in the circuit

b) steps up the line voltage

c) steps-down the line voltage

d) chokes low frequency current

Answer: (a)

Question : 2

In semiconductors, at room temperature

a) the valence band is partially empty and the conduction band is partially filled

b) the valence band is completely filled and the conduction band is partially filled

c) the conduction band is completely empty

d) the valence band is completely filled

Answer: (b)

In semiconductros, the conduction is empty and the valence band is completely filled at 0 K. No electron from valence band can cross over to conduction band at 0K.

But at room temperature some electrons in the valence band jump over to the conduction band due to the small forbidden gap.

i.e. 1 eV.

Question : 3 [PCS (Pre) 2016]

Nickel-Cadmium (Ni-Cd) battery is used in

a) Transistors

b) Calculator

c) Cordless electronic appliances

d) All of the above

Answer: (d)

Question : 4

Zener breakdown takes place if

a) doped impurity is high

b) less impurity in n-part

c) doped impurity is low

d) less impurity in p-part

Answer: (a)

Zener breakdown can occur in heavily doped diodes. In lightly doped diodes the necessary voltage is higher, and avalanche multiplication is then the chief process involved.

Question : 5

When n-type semiconductor is heated

a) number of holes increases while that of electrons decreases

b) number of electrons and holes remain same

c) number of electrons increases while that of holes decreases

d) number of electrons and holes increases equally

Answer: (d)

Due to heating, when a free electron is produced then simultaneously a hole is also produced.

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