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ECE :: Electronic Devices and Circuits

  1. The current through a PN Junction diode with v volts applied to the P region to the N region, where (I0 is the reverse saturation current to the diode, m the ideality factor, k the Boltzmann constant, T the absolute temperature and q the magnitude of charge on an electron) is

  2. A.
    I0 (e-qv/mkT - 1)
    B.
    I0 e-qv/mkT
    C.
    I0 (1 - eqv/mkT)
    D.
    I0 (eqv/mkT - 1)

  3. The ratio of diffusion constant for hole DP to the mobility for holes is proportional to

  4. A.
    T2
    B.
    T
    C.
    1/T
    D.
    T3

  5. The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300k will be (in m2/s).

  6. A.
    0.43
    B.
    0.16
    C.
    0.04
    D.
    0.01

  7. During induction heating of metals which of the following is abnormally high?

  8. A.
    Frequency
    B.
    Voltage
    C.
    Current
    D.
    Power factor

  9. Assertion (A): Alkali metals are used as emitters in phototubes.

    Reason (R): Alkali metals have low work functions.

  10. A.
    Both A and R are true and R is correct explanation of A
    B.
    Both A and R are true but R is not a correct explanation of A
    C.
    A is true but R is false
    D.
    A is false but R is true

  11. The output v-i characteristics of enhancement type MOSFET has

  12. A.
    only an ohmic region
    B.
    only a saturation region
    C.
    an ohmic region at low voltage value and a saturation region at high voltage
    D.
    a saturation region at low voltage value and an ohmic region at high voltage

  13. In a full wave rectifier, the current in each of the diodes flows for

  14. A.
    the complete cycle of the input signal
    B.
    half cycle of the input signal
    C.
    less than half cycle of the input signal
    D.
    one-fourth cycle of the input signal

  15. In an ideal junction transistor the impurity concentration in emitter (E ), base (B) and collector (C) is such that

  16. A.
    E > B > C
    B.
    B > C > E
    C.
    C > E > B
    D.
    C = E = B

  17. The rating of a transformer to deliver 100 watts of D.C. power to a load under half wave rectifier will be nearly

  18. A.
    1 kVA
    B.
    350 VA
    C.
    175 VA
    D.
    108 VA

  19. When a p-n junction is forward biased, the current remains zero till the applied voltage overcomes the barrier potential.

  20. A.
    True
    B.
    False