A single layer air cored coil has n turns and inductance L. If a new coil is for

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Question
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

Correct Answer

4 L

Explanation

Inductance is proportional to square of number of turns.

Materials and Components problems

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1. 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

2. 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

3. 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

4. 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 =

5. 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)

6. 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

7. 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

8. The units for electric dipole moment are
Options
A. coulombs
B. colomb-metre
C. coulomb/metre
D. coulomb/m²

10. Assertion (A): Copper is a good conductor of electricity.
Reason (R): Copper has a face centred cubic lattice.
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

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