A parallel plate capacitor has its length, width and separation doubled. It frin

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Question
A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neglected, to keep the capacitance same, the dielectric constant must be
Options
A. halved
B. kept the same
C. doubled
D. made 4 times

Correct Answer

halved

Explanation

A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neg

. When dimensions are changed, A become four times and d becomes twice.

Since ?₀ is constant, ?_r must be halved to keep C constant.

Materials and Components problems

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1. For a permanent magnetic material
Options
A. the residual induction and coercive field should be large
B. the residual induction and coercive field should be small
C. area of hysteresis loop should be small
D. initial relative permeability should be high

2. If n denotes principal quantum number, the angular quantum number l = 0, 1... (n - 1).
Options
A. True
B. False

3. Above ferroelectric curie temperature, spontaneous polarization in ferroelectric materials becomes stronger.
Options
A. True
B. False

4. If e is the charge of an electron, R is the radius of its orbit and ? is the angular velocity of electron, the magnetic dipole moment ?_m of the orbit is |?_m| = e?R².
Options
A. True
B. False

5. Material which lack permanent magnetic dipoles are known as
Options
A. paramagnetic
B. diamagnetic
C. ferromagnetic
D. ferrimagnetic

8. 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 I_th = SA₀ T² e^-Ew/kT.
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

9. Assertion (A): From the slope of the line in Figure, we can find permanent dipole moment of the molecules.
Reason (R): Total polarization of a polyatomic gas is given by P = N(a_e + a_i + ?²_p / 3kT)E.
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

10. Assertion (A): Electronic and Ionic polarization in a polyatomic gas are independent of temperature.
Reason (R): The orientation polarization is independent of 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

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