Assertion (A): In some materials, ?r is independent of temperature while in othe

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Question
Assertion (A): In some materials, ?_r is independent of temperature while in others, ?_r depends on temperature.
Reason (R): If permanent dipoles are absent, ?_r varies with temperature.
Options
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

Correct Answer

A is true but R is false

Materials and Components problems

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1. Figure shows a composite capacitor. If C_A, C_B, C_C are the capacitances of capacitors A, B, C, the overall capacitance C is
Options
A. C = C_A + C_B + C_C
B. C = (C_A + C_B) C_C
C. C =
D. C =

2. For a core having a relative permeability ?_r, magnetic dipole moment per unit volume M and field strength H, the flux density B is
Options
A. B = ?_r (H + M)
B. B = ?₀ (H + M)
C. B = ?₀?_r (H + M)
D. B = ?₀?_r (H - M)

4. Assertion (A): Dielectric losses are proportional to tan ?.
Reason (R): tan ? = where ?_r^' and ?_r^" denote the real and imaginary parts of ?_r.
Options
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

5. An electron shell corresponding to principal quantum number n can contain a maximum of
Options
A. n² electrons
B. 2n² electrons
C. 2n electron
D. n³ electron

6. The direction of force an a conductor carrying current and lying in a magnetic field can be found by using
Options
A. Fleming's left hand rule
B. Fleming's right hand rule
C. Cork screw rule
D. Any of the above

7. The real part of complex dielectric constant and tan? for a dielectric are 2.1 and 5 x 10^-4 at 100 Hz respectively. The imaginary part of dielectric constant at 100 Hz is
Options
A. 1.05 x 10^-3
B. 2.1 x 10^-3
C. 5 x 10^-3
D. 1.05 x 10^-2

8. 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
Options
A. 0.5 L
B. L
C. 2 L
D. 4 L

9. In anti-ferromagnetic materials, the graph of susceptibility versus temperature shows a sharp maximum at a certain temperature. This temperature is known as
Options
A. Curie temperature
B. Neel temperature
C. Weiss temperature
D. Bitter temperature

10. When the atom of rare gas is placed in an electric field the nucleus shifts from the centre of electron cloud by an amount x. If the radius of electron cloud is R, then
Options
A. x << R
B. x ≂ 0.5 R
C. x ? 0.75 R
D. x ? R

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