Assertion (A): In a perfect capacitor, the current density is given by ? ?0E0?'r

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Question
Assertion (A): In a perfect capacitor, the current density is given by ? ?₀E₀?^'_rcos(?t + 90�), where ?_r^' is real part of dielectric constant.
Reason (R): In a perfect capacitor, dielectric losses are zero.
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

Both A and R are true and R is correct explanation of A

Explanation

If dielectric losses are zero, the current in capacitor leads the applied voltage by 90�.

Also imaginary part of is ?_r is zero.

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2. 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

3. 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

4. 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

6. The attraction between the nucleus and valence electron of copper atom is
Options
A. zero
B. weak
C. strong
D. either zero or strong

7. The minority carrier life time and diffusion constant in a semiconducting material are 100 ?s and 100 cm²/s respectively. The diffusion length of carriers is
Options
A. 0.1 cm
B. 0.01 cm
C. 0.0141 cm
D. 1 cm

8. If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature
Options
A. both will have equal value of resistivity
B. both will have equal negative resistivity
C. resistivity of germanium will be higher than that of silicon
D. resistivity of silicon will be higher than that of germanium

10. If a piece of wood is placed in a magnetic field
Options
A. the magnetic field will not be affected
B. the magnetic lines of force will bend towards the piece
C. the magnetic lines of force will bend away from the piece
D. the flux may increase or decrease

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