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ECE Objective Questions { Semiconductor Physics and Diodes }

22.  When bias applied to a van-cap diode is increased, its capacitance
A. is decreased
B. is increased
C. remains constant
D. first increases and then decreases

23. A light-emitting diode can be made from
A. phosphorescent material
B. germanium
C. silicon
D. gallium arsenid

24. A phototube is an electronic tube
A. whose resistance decreases as its cathode is exposed to more light
B. that emits photoelectrons when its cathode is illuminated
C. which is used for producing a brilliant flash of light for taking photographs in the dark
D. that is used in TV sets for producing picture on the screen

25. For converting a piece of pure silicon into a P-type extrinsic semiconductor, you will add an extremely small quantity of
A. antimony
B. phosphorous
C. arsenic
D. boron

26. The maximum reverse voltage that can be applied to an ordinary semiconductor diode without irreversible damage is called
A. peak inverse voltage
B. Zener voltage
C. avalanche breakdown voltage
D. cut-off voltage

27. Addition of impurity in the ratio of 1 in 108 to a pure or intrinsic semiconductor
A. decreases its conductivity nearly 100 times
B. increases its conductivity nearly 108 times
C. increases its conductivity nearly 100 times
D. increases its resistivity nearly 100 times

28. In a P-type semiconductor, free electrons
A. form majority carriers
B. take no part in conduction
C. equal the number of holes
D. form minority carriers

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