Electronics and Communication Engineering - Materials and Components

21. 

Semiconductors have a positive temperature coefficient of resistivity.

A. True
B. False

Answer: Option B

Explanation:

In semiconductors the temperature coefficient of resistivity is negative.


22. 

From a homogeneous and isotropic dielectric material of dielectric constant ∈r, a small volume element is taken out creating a cavity. The field can be kept homogeneous if Di. (i.e., electric flux density inside the cavity) and D0 (i.e., electric flux density outside the cavity) are such that

A. D0 = Di
B.
C.
D. either (a) or (b)

Answer: Option B

Explanation:

Since the field is homogeneous .


23. 

An electrolytic capacitor can be used for

A. ac only
B. dc only
C. both ac and dc
D. high frequency ac

Answer: Option B

Explanation:

No answer description available for this question. Let us discuss.

24. 

Figure shows a composite capacitor. If CA, CB, CC are the capacitances of capacitors A, B, C, the overall capacitance C is

A. C = CA + CB + CC
B. C = (CA + CB) CC
C. C =
D. C =

Answer: Option C

Explanation:

B and C are in series and A is in parallel with this combination.


25. 

As regards ferromagnetic Curie temperature Qf and paramagnetic curie temperature θ

A. Qf > θ
B. θ > Qf
C. θ equal to or less than Qf
D. θ may be equal to less than or more Qf

Answer: Option B

Explanation:

No answer description available for this question. Let us discuss.