Electronics and Communication Engineering - Materials and Components

26. 

If a capacitor C having selectivity factor Q is scaled down in all its dimensions by a factor K without any altering the dielectric material, the new capacitor will have capacitance and selectivity as

A. C,
B. , Q
C. ,
D. C, K

Answer: Option B

Explanation:

Since the dimension of plates is scaled down by K, the area decreases by a factor of K2, the distance between plates decreases by a factor of K.

Therefore, capacitance changes to .

The selectivity will not be affected.


27. 

The hysteresis loss is

A. proportional to frequency
B. independent of frequency
C. proportional to (frequency)2
D. proportional to

Answer: Option A

Explanation:

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

28. 

If m, v, r are the mass, velocity and radius of orbit of electron and h is Planck's constant, quantum condition for electron's orbit is

A.
B.
C.
D.

Answer: Option B

Explanation:

For stable circular orbit angular momentum is equal to integer times .


29. 

Assertion (A): For a magnetic material M = (μr - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and μr is relative permeability.

Reason (R): μr can have any value from 0 to hundreds of thousands.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

Answer: Option C

Explanation:

μr is always more than 1. It cannot be 0 or less than 1.


30. 

As regards ∈0 and ∈r (absolute and relative permittivity)

A. both ∈0 and ∈r can be interpreted in terms of atomic properties of medium
B. only ∈r can be interpreted in terms of atomic properties of medium
C. only ∈0 can be interpreted in terms of atomic properties
D. r has no physical significance

Answer: Option B

Explanation:

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