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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 4
21.

Assertion (A): The forward resistance of a p-n diode is not constant.

Reason (R): The v-i characteristics of p-n diode is non-linear.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

If v-i characteristics is non linear, the ratio v-i is not constant.

22.
For a photoengraving the mask used is
master mask
slave mask
working mask
photo mask
Answer: Option
Explanation:

The mask that is prepared first is called the master mask made from glass substrates covered by thin chromium film.

From the master masks are prepared working masks by contact pointing and used for Photolithography which means Photo engraving.

23.
In a varactor diode the increase in width of depletion layer results in
decrease in capacitance
increase in capacitance
no change in capacitance
either (a) or (b)
Answer: Option
Explanation:

Capacitance is inversely proportional to distance between plates.

24.
In given figure a silicon diode is carrying a constant current of 1 mA. When the temperature of the diode is 20°C, VD is found to be 700 mV. If the temperature rises to 40°C, VD becomes approximately equal to
747 mV
660 mV
680 mV
700 mV
Answer: Option
Explanation:

Id = Io(eVD/ηVT - 1)

By considering , then

= eVD/ηVT

Id is constant according to question,

VD a T

.

25.
The work function of a photo surface whose threshold wave length is 1200 A, will be
0.103 eV
0.673 eV
1.03 eV
1.27 eV
Answer: Option
Explanation:
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