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Electronics and Communication Engineering - Materials and Components

Exercise : Materials and Components - Section 5
26.
As per Matthiessen's rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures
aT = 0
aT > ri
aT ∼ ri
aT < ri
Answer: Option
Explanation:

At very low temperatures a T → 0. Since resistivity has a finite value even at low temperature, a T < ri.

27.
Consider the following statement: In case of a superconductor
  1. B = 0
  2. μr is high
  3. diamagnetism is high
  4. transition temperature varies with isotopic mass.
Of the above statements
1 and 2 are correct
2, 3, 4 are correct
1, 3, 4 are correct
2, 4 are correct
Answer: Option
Explanation:
No answer description is available. Let's discuss.
28.

Assertion (A): In liquids and glassy substances, dielectric losses occur.

Reason (R): The orientation polarization in many substances is frequency dependent.

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:
No answer description is available. Let's discuss.
29.
A single layer air cored coil has n turns and inductance L. If a new coil is formed by having 2n turns while keeping the coil length and diameter the same, the new inductance is
0.5 L
L
2 L
4 L
Answer: Option
Explanation:

Inductance is proportional to square of number of turns.

30.
The colour code on a carbon resistor is yellow-violet-orange. The value of resistance is
17000 Ω
27000 Ω
37000 Ω
47000 Ω
Answer: Option
Explanation:
No answer description is available. Let's discuss.
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