EDC Questions

1.State the principle of operation of SCR?

A silicon controlled rectifier is a semi conductor device that acts as a true electronic switch. It can change alternating current in to direct current and at the same time it can control the amount of power fed to the load. Thus SCR combines the features of a rectifier and a transistor.

2.Distinguish pinch off and cut off in FET?

Pinch off voltage – It is the minimum drain-source voltage at which the drain current essentially becomes constant. Cut-off voltage – It is the gate source voltage where the channel completely cut off and the drain current becomes zero.

3.Distinguish CB, CE, CC configurations in Transistors?

Common base configuration - If the base terminal is connected common to the input and output , it is called common base. The input is fed between the emitter and base and the out put between the collector and base. CE configuration – If the emitter is common to both input and output , it is called CE configuration. Here input is applied between base and emitter and output is taken from collector and emitter. CC configuration – If the collector is common to both input and output , it is called CC configuration. Here input is applied between base and collect or and output is taken from emitter and collector.

4. Discuss the applications of SCR?

In many applications SCR is used as a power control device. The common

applications includes

1. Relay control

2. Regulated power supplies

3. Static switches

4. Motor control

5. Inverters

6. Battery chargers

7. Heater control


5. A silicon diode measures a low value of resistance with the meter leads in both positions. The trouble, if any, is
A. the diode is open.
B.the diode is shorted to ground.
C.the diode is internally shorted.
D.the diode is working correctly.


6. Single-element semiconductors are characterized by atoms with ____ valence electrons.
A.3
B.4
C.5
D.2
E.none of the above


7. Under normal conditions a diode conducts current when it is
A.reverse-biased.
B.forward-biased.
C.avalanched.
D.saturated.


8. A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.
A.positive supply
B.negative supply
C.Cathode
D.anode


9. As the forward current through a silicon diode increases, the internal resistance
A.increases.
B.decreases.
C.remains the same.