Power Semiconductor Devices and Their Applications MCQs

Question 1

The latching current of SCR is 18 mA. Its holding current will be

Accepted Answer

6 mA

Answer

18 mA

Answer

54 mA

Answer

12 mA

Question 2

Apositive voltage is applied to the gate of a reverse biased SCR.

Accepted Answer

This increases reverse leakage current into anode

Answer

This injects more electrons into junction J1

Answer

Resting of junction is unaffected

Answer

Failure of junctions occurs due to thermal runaway.

Question 3

At a room temperature of 30 ?C, minimum voltage and current required to fire a SCR is

Accepted Answer

3V, 40 mA

Answer

0.6 V, 40 mA

Answer

no limit

Answer

3 V,100 mA

Question 4

When the SCR conducts, the forward voltage drop

Accepted Answer

is 1 to 1.5 V decreases slightly with load current

Answer

is 0.7 V

Answer

remains constant with load current

Question 5

The turn-on time of a SCR with inductive load is 20 pis. The pulse train frequency is 2.5 kHz with a mark/space ratio of ?10 , then

Accepted Answer

the SCR will turn on

Answer

the SCR will not turn on

Answer

the SCR will turn on if inductance is removed

Answer

the SCR will turn on if pulse frequence is increased to two times.

Question 6

Which of the following PNPN device has a terminal for synchronising purpose?

Accepted Answer

SUS

Answer

Diac

Answer

Triac

Answer

Schmitt trigger

Question 7

The device which cannot be triggered by voltage of either polarity is

Accepted Answer

SUS

Answer

Diac

Answer

Triac

Answer

Schotkey diode

Question 8

The maximum ? in a SGR is

Accepted Answer

directly proportional to Vm of supply voltage

Answer

inversely proportional to Vm of supply voltage

Answer

directly proportional to L in the circuit

Answer

directly proportional to L in the circuit

Question 9

A SCR fires at a minimum current of 80 mA and ? 65 ?C. The minimum current required to fire at 25?C is

Accepted Answer

half of 80 mA

Answer

> 80 mA

Answer

equal to 80 mA

Answer

< 80 mA