1. The maximum efficiency of a half wave rectifier is ?

0.3333

0.4067

0.6667

0.729

Answer: 0.4067

Explanation:


2. To eliminate the crossover distortion, the transistors are given at their bases ?

small forward bias

self bias

large current

smaller current

Answer: small forward bias

Explanation:


3. Static electricity is produced by ?

chemical reaction

friction

induction

both friction and induction

Answer: friction

Explanation:


4. The gain of a CE amplifier is highest at ?

low frequencies

mid frequencies

high frequencies

All frequencies

Answer: mid frequencies

Explanation:


5. synchronous motor will stop when ?

load in motor varies

supply voltage fluctuates

excitation winding gets disconnected

supply voltage frequency changes

Answer: excitation winding gets disconnected

Explanation:


6. While starting a synchronous motor as induction motor, field winding is ?

kept open-circuited

short-circuited by low resistance

connected to D.C. supply

None of these

Answer: short-circuited by low resistance

Explanation:


7. While a synchronous generator is supplying a zero power factor lagging load the armature reaction will be ?

De magnetizing

Magnetizing

Cross magnetizing

Nothing

Answer: Magnetizing

Explanation:


8. In a synchronous motor, the negative phase sequence exists when the motor is ?

under-loaded

supplied with unbalanced voltage

over-loaded

None of these

Answer: supplied with unbalanced voltage

Explanation:


9. Synchronous motor only runs at ?

less than synchronous speed

more than synchronous speed

the synchronous speed

None of these

Answer: the synchronous speed

Explanation:


10. If the synchronous motor, properly synchronized to the supply is running on no load and is having negligible loss then ?

the stator current will be very small

the stator current will be zero

the stator current will be very high

the back e.m.f. will be more than the supply voltage

Answer: the stator current will be zero

Explanation: