# Electronics and Communication Engineering - Materials and Components

### Exercise :: Materials and Components - Section 3

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

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

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.

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

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