MCQs on Electronic Science - 1

1. Biasing is done in class A mode to

(A) Save power
(B) Improve stability
(C) Reduce number of sources
(D) Both (B) and (C)



2. The critical inductance in mains power supply ensures that the current through ‘L’ never becomes zero. For this, critical value of inductance is

(A) RL/310
(B) RL/450
(C) RL/620
(D) RL/942



3. A tree in a network has a

(A) Closed path
(B) No closed path
(C) No nodes
(D) No branches


4. Which is a three-terminal negative voltage regulator IC?

(A) 78 XX
(B) IC 723
(C) LM 317
(D) 79 XX



5. An antenna, when radiating, has a highly directional radiation pattern. When the antenna is receiving, its radiation pattern

(A) Is more directive
(B) is less directive
(C) is same that of transmitting antenna
(D) Exhibits no directivity at all.



6. In optical fiber communications

I. Inter modal dispersion can be avoided by using SMF.
II. Inter modal dispersion can be avoided by using MMF.
III. Third transmission window wavelength is used to avoid Rayleigh scattering losses.
IV. 800-900 nm window is used to avoid Rayleigh’s scattering losses.

Codes:
(A) Options II and III are correct.
(B) Options II and IV are correct.
(C) Options I and III are correct.
(D) Options IV and I are correct.



7. The modulation index of an AM wave in changed from 0 to 1. The transmitted power is

(A) Unchanged
(B) Halved
(C) Doubled
(D) Increased by 50 percent



8. Indicate the false statement. The square of the thermal noise voltage generated by a resistor is proportional to

(A) Its temperature
(B) Its resistance
(C) Boltzmann constant
(D) The bandwidth over which it is measured


9. The output of a dc motor depends mainly on

(A) Speed and torque
(B) Speed and back emf
(C) Speed and applied voltage
(D) Speed and load resistance


10. Which one of the following is an adjustable IC voltage regulator?

(A) IC 7824
(B) IC 7912
(C) LM 338
(D) IC 7808

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