Electronics and Communication Engineering - Materials and Components

Exercise :: Materials and Components - Section 1

36.

Assertion (A): At a temperature of 1000 K, thermionic emission current is about 0.1 A/cm2 of surface.

Reason (R): Thermionic emission current is given by Ith = SA0 T2 e-Ew/kT.

 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:

If different values are substituted in the equation for Ith the value of emission current comes out to be about 0.1 A/cm2.

37.

At room temperature, the current in intrinsic semiconductor is due to

 A. holes B. electrons C. ions D. holes and electrons

Explanation:

Both electrons and holes contribute to flow of current in semiconductors.

38.

Ferroelectric materials are those which

 A. cannot be polarized B. have a permanent polarization C. have ae equal to zero D. have μp = 0

Explanation:

Ferroelectric materials have permanent polarization.

39.

Assertion (A): Power loss in a conductor of resistance P = I2R.

Reason (R): When a conductor is carrying current with current density J as a result of applied field E, then heat developed/m3/ second = JE.

 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:

Heat developed depends an power loss.

40.

Assertion (A): For Diamond, μr = 1

Reason (R): Diamond is a diamagnetic material.

 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