ELECTRONICS CHAPTER 6 3

When the temperature increases, the inter-base resistance of a UST

• remains unchanged

• increases

• decreases

• is zero

When checking a good SCR or TRIAC with an ohmmeter you will

• Show low resistance with positive on anode and negative on cathode, and high resistance when reversed

• Show high resistance with negative on anode and positive on cathode, and low resistance when reversed

• Show high resistance in both directions

• Show low resistance in both directions

When testing an SCR with an ohmmeter, the SCR will conduct if what two elements are shorted together?

• Gate and Anode

• Ground and Cathode

• Gate and Ground

• Gate and Cathode

Shockley diode is usually used as trigger for

• SCR

• Diac

• Triac

• SCS

When the firing angle of SCR is increased, its output

• decreases

• increases

• remains unchanged

• doubles

The conducting triac is turned off by removing the ______ voltage or by _______

• Cathode, reversing polarity

• Gate, reversing polarity

• Main terminal, reversing polarity

• Anode, reversing polarity

In a parallel inverter

• each thyristor is turned on twice during each cycle LLO

• each thyristor is turned on once during each cycle

• each thyristor is turned on either once or twice in each load cycle

• each thyristor may be turned on upto four times in each load cycle

To turn on the UT, the forward bias on emitter diode should be ________ the peak point voltage.

• more than

• less than

• equal to

• twice

An SCR with two gate terminals is called a

• SCS

• Diac

• FLD

• Zener

What device is a bidirectional thyristor used as a breakover device?

• Diac

• Shockley diode

• Zener diode

• UST