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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.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
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
holes
electrons
ions
holes and electrons
Answer: Option
Explanation:

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

38.
Ferroelectric materials are those which
cannot be polarized
have a permanent polarization
have ae equal to zero
have μp = 0
Answer: Option
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.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

Heat developed depends an power loss.

40.

Assertion (A): For Diamond, μr = 1

Reason (R): Diamond is a diamagnetic material.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

For diamagnetic materials μr = 1.

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