**OSCILLATORS Questions with Answers :-**

**1. An oscillator converts ……………..**

- c. power into d.c. power
- c. power into a.c. power
- mechanical power into a.c. power
- none of the above

Answer : 2

**2. In an LC transistor oscillator, the active device is ……………**

- LC tank circuit
- Biasing circuit
- Transistor
- None of the above

Answer : 3

**3. In an LC circuit, when the capacitor is maximum, the inductor energy is ……….**

- Minimum
- Maximum
- Half-way between maximum and minimum
- None of the above

Answer : 1

**4. In an LC oscillator, the frequency of oscillator is ……………. L or C.**

- Proportional to square of
- Directly proportional to
- Independent of the values of
- Inversely proportional to square root of

Answer : 4

**5. An oscillator produces……………. oscillations**

- Damped
- Undamped
- Modulated
- None of the above

Answer : 2

**6. An oscillator employs ……………… feedback**

Positive

Negative

Neither positive nor negative

Data insufficient

Answer : 1

**7. An LC oscillator cannot be used to produce ……………….. frequencies**

High

Audio

Very low

Very high

Answer : 3

**8. Hartley oscillator is commonly used in ………………**

Radio receivers

Radio transmitters

TV receivers

None of the above

Answer : 1

**9. In a phase shift oscillator, we use …………. RC sections**

Two

Three

Four

None of the above

Answer : 2

**10. In a phase shift oscillator, the frequency determining elements are …………**

L and C

R, L and C

R and C

None of the above

Answer : 3

**11. A Wien bridge oscillator uses ……………. feedback**

Only positive

Only negative

Both positive and negative

None of the above

Answer : 3

**12. The piezoelectric effect in a crystal is ……………**

A voltage developed because of mechanical stress

A change in resistance because of temperature

A change in frequency because of temperature

None of the above

Answer : 1

**13. If the crystal frequency changes with temperature, we say that crystal has ………….. temperature coefficient**

Positive

Zero

Negative

None of the above

Answer : 1

**14. The crystal oscillator frequency is very stable due to ………………. of the crystal**

Rigidity

Vibrations

Low Q

High Q

Answer : 4

**15. The application where one would most likely find a crystal oscillator is ……………..**

Radio receiver

Radio transmitter

AF sweep generator

None of the above

Answer : 2

**16. An oscillator differs from an amplifier because it ………**

Has more gain

Requires no input signal

Requires no d.c. supply

Always has the same input

Answer : 2

**17. One condition for oscillation is ………….**

A phase shift around the feedback loop of 180o

A gain around the feedback loop of one-third

A phase shift around the feedback loop of 0o

A gain around the feedback loop of less than 1

Answer : 3

**18. A second condition for oscillations is ……………….**

A gain of 1 around the feedback loop

No gain around the feedback loop

The attention of the feedback circuit must be one-third

The feedback circuit must be capacitive

Answer : 1

**19. In a certain oscillator Av = 50. The attention of the feedback circuit must be …………**

1

01

10

02

Answer : 4

**20. For an oscillator to properly start, the gain around the feedback loop must initially be**

1

Greater than 1

Less than 1

Equal to attenuation of feedback circuit

Answer : 2

**21. In a Wien-bridge oscillator, if the resistances in the positive feedback circuit are decreased, the frequency……….**

Remains the same

Decreases

Increases

Insufficient data

Answer : 3

**22. In Colpitt’s oscillator, feedback is obtained …………….**

By magnetic induction

By a tickler coil

From the centre of split capacitors

None of the above

Answer : 3

**23. The Q of the crystal is of the order of …………**

100

1000

50

More than 10,000

Answer : 4

**24. Quartz crystal is most commonly used in crystal oscillators because ………….**

It has superior electrical properties

It is easily available

It is quite inexpensive

None of the above

Answer : 1

**27. ………….. is a fixed frequency oscillator**

Phase-shift oscillator

Hartely-oscillator

Colpitt’s oscillator

Crystal oscillator

Answer : 4

**28. In an LC oscillator, if the value of L is increased four times, the frequency of oscillations is …………**

Increased 2 times

Decreased 4 times

Increased 4 times

Decreased 2 times

Answer : 4

**29. An important limitation of a crystal oscillator is ……………**

Its low output

Its high Q

Less availability of quartz crystal

Its high output

Answer : 1

**30. The signal generator generally used in the laboratories is ………….. oscillator**

- Wien-bridge
- Hartely
- Crystal
- Phase shift

Answer : 1