1. A diac is used to ?

trigger a triac

commutate a triac

increase efficiency of a triac

protect a triac

Answer: trigger a triac

Explanation:


2. R-C triggering is preferred over resistance triggering process because it provides ?

larger value of firing angle

protects the device from getting damaged

causes quick triggering

provides accurate firing

Answer: larger value of firing angle

Explanation:


3. In the reverse biased condition of an SCR ?

two out of three junctions are reverse biased

one out of three junctions is reverse biased

all the three junctions are reverse biased

all the three junction are forward biased

Answer: two out of three junctions are reverse biased

Explanation:


4. A light activated silicon controlled rectifier is a ?

four-layer four-junction device

four-layer three-junction device

three-layer two-juction device

two-layer two-junction device

Answer: four-layer three-junction device

Explanation:


5. A triac behaves like two ?

inverse parallel-connected SCRs with common gate

resistors and one diode

four-layer diodes in parallel

diodes in series

Answer: inverse parallel-connected SCRs with common gate

Explanation:


6. The value of peak point current of a UJT is ?

very high

very low

high

about 1.5 times that of valley point current

Answer: very low

Explanation:


7. A triac can be fired ?

only by the negative half cycle of the supply

only by the positive half cycle of the supply

both by the positive as well as the negative half cycles of the supply

without any biasing

Answer: both by the positive as well as the negative half cycles of the supply

Explanation:


8. After firing an SCR, the gating pulse is removed. The current in the SCR will remain ?

the same

rise a little and then fall to zero

immediately fall to zero

rise up

Answer: the same

Explanation:


9. A thyristor can be turned off by ?

reducing the anode current below holding current value

reversing the anode voltage

both A. and B.

none of the above.

Answer: both A. and B.

Explanation:


10. An inverter, as compared to oscillators, provides output ?

noiseless

distortionless

low voltage

low frequency

Answer: low frequency

Explanation: