JEE Main 2015 · 10 Apr · Shift 1 · Physics Q15

← JEE Main 2015 · 10 Apr · Shift 1

PhysicsSingle correct+4 / -1Question 15 of 90

Shown in the figure are two point charges +Q and −Q inside the cavity of a spherical shell. The charges are kept near the surface of the cavity on opposite sides of the centre of the shell. If $\sigma_1$ is the surface charge on the inner surface and $Q_1$ net charge on it and $\sigma_2$ the surface charge on the outer surface and $Q_2$ net charge on it then :

A thick shaded spherical shell with a cavity containing +Q near the top and −Q near the bottom of the cavity.

\sigma_1\ne0,\ Q_1\ne0

;

\sigma_2\ne0,\ Q_2\ne0

\sigma_1\ne0,\ Q_1=0

;

\sigma_2\ne0,\ Q_2=0

\sigma_1\ne0,\ Q_1=0

;

\sigma_2=0,\ Q_2=0

\sigma_1=0,\ Q_1=0

;

\sigma_2=0,\ Q_2=0

Answer and worked solution

Official answer: C

The total charge in the cavity is zero, so the inner surface carries $Q_1=0$ . But the charges are off-centre, so the induced density $\sigma_1$ varies and is non-zero.

The outer surface is shielded from the cavity, so $\sigma_2=0$ and $Q_2=0$ .

Topics:Conductors and charge distribution

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JEE Main 2015 · 10 Apr · Shift 1, Physics question 15