Electronics and Communication Engineering - Materials and Components

31. 

For a paramagnetic material, susceptiblity increases with increasing temperature.

A. True
B. False

Answer: Option B

Explanation:

Susceptibility ∝ .


32. 

Hydrogen is used in

A. large size transformers
B. MCB
C. large size generators
D. circuit breakers

Answer: Option C

Explanation:

Modem large size generators have hydrogen cooling.


33. 

Assertion (A): Ferroelectric materials have spontaneous polarization.

Reason (R): Above curie temperature, ∈ = for ferro-electric materials.

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 B

Explanation:

Both A and R are correct. Spontaneous polarization vanishes above ferroelectric curie temperature.


34. 

If e is the charge of an electron, R is the radius of its orbit and ω is the angular velocity of electron, the magnetic dipole moment μm of the orbit is |μm| = eωR2.

A. True
B. False

Answer: Option B

Explanation:

1 μm 1 = 0.5 eωr2.


35. 

If ∈r' and ∈r" are the real and imaginary parts of complex dielectric constant ∈r, and δ is the loss angle. Then

A.
B.
C. tan δ = ∈'"
D. tan δ = 1 - ∈'

Answer: Option B

Explanation:

If ∈r" = 0, δ = 0.