Competitive Exams: Physics MCQs (Practice-Test 25 of 35)

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  1. An electronic oscillator gives sustained oscillations when the feedback is

    1. negative and out of phase with the input

    2. negative and in phase with the input

    3. positive and, out of phase with. The input

    4. positive and in phase with the input

  2. A zener diode is also a p-n junction diode. It can be used as a/an

    1. half-wave rectifier

    2. full-wave rectifier

    3. ac voltage regulator

    4. dc voltage regulator

  3. A transistor is operated in CB mode. If the collector base voltage is reduced to zero keeping the input current undisturbed, the output will be

    1. zero

    2. a little higher than the input current

    3. equal to the input current

    4. a little less then the input current

  4. The circuit of a common emitter transistor amplifier with conventional stabilized bias is shown in the figure. In this circuit, R l and R 2

    1. as well as Re forward bias the base-emitter junction

    2. forward bias the base miter junction but Re reverse biases the base-emitter junction

    3. reverse bias the base-emitter junction but Re forward biases the base-emitter junction

    4. as well as Re reverse bias the base-emitter junction

  5. The overall gain of a two-stage amplifier is 80 dB, If the voltage gain of the, first stage is 100, then the voltage gain of the second stage is:

    1. Gain 20

    2. Gain 100

    3. Gain 180

    4. Gain 8000

  6. The equivalent electrical circuit of a vibrating crystal is as shown below: The expression for the resonance frequency of this circuit is

    1. Equi 1/2p-p LC

    2. Equi 1/2p-p L (C + Cm)

    3. Equi 1/2p-C + C m/LC Cm

    4. Equi 1/2p-R (C + Cm)