Electronics and Communication Engineering - Materials and Components

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

Answer: Option A

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

Answer: Option D

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

Answer: Option B

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

Answer: Option A

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

Answer: Option A

Explanation:

For diamagnetic materials μr = 1.