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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 4
6.
A Si sample is doped with a fixed number of group N impurities. The electron density n is measured from 4 K to 1200 k for the sample. Which one of the following is correct?
n remains constant over the temperature range
n increases monotonicaliy with increasing temp
n increases first remains constant over a range and again increases with increasing temperature
n increases show a peak and then decrease with temperature
Answer: Option
Explanation:
No answer description is available. Let's discuss.
7.

Assertion (A): In design of circuit using BJT, a derating factor is used.

Reason (R): As the ambient temperature increases, heat dissipation becomes slower.

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:

Increase of ambient temperature lowers the heat dissipation capacity.

Therefore derated operation of BJT is necessary lest BJT should be destroyed.

8.
If the drift velocity of holes under a field gradient of 100 V/m is 5m/sec. Their mobility is
0.05
0.5
50
500
Answer: Option
Explanation:

E = μ . Vd μ =.

9.
In a P type silicon sample, the hole concentration is 2.25 x 1015 / cm3. If the intrinsic carrier concentration is 1.5 x 1010/ cm3 the electron concentration is
zero
1010/cm3
105/cm3
1.5 x 1025/cm3
Answer: Option
Explanation:

Electron concentration .

10.
The behaviour of a JFET is similar to that of
NPN transistor
PNP transistor
SCR
Vacuum triode
Answer: Option
Explanation:

Both JFET and vacuum triode are voltage controlled devices.

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