Question

The variation of the magnitude of the electric field with radial distance r due to a given configuration is depicted in the accompanying figure. The configuration could be

• A. thick spherical conducting shell with a point charge at its centre.
• B. thick spherical dielectric shell with a point charge at its centre.
• C. conducting sphere with surface charge.
• D. two neutral concentric thin conducting shells with a point charge at the centre.

Answer 1

The correct option is A thick spherical conducting shell with a point charge at its centre.

From the graph pattern ,we observe that $E\propto \frac{1}{r^n}$ where $n\ge 1$

Now, we see that the field $E$ suddenly becomes $0$ for some small interval and again catches up with usual graph.

Now, inspecting for options, we get:-

$\left(A\right)$:-It should be a charge placed at the center of a thick spherical conducting shell. The $0$ field is because in the conductor there is no field when charges are at rest.

$\left(B\right)$:-The shell can't be dielectric , otherwise field would not be $0$.

$\left(C\right)$:-Conducting sphere with surface charge does not have field inside the shell and hence such graph is not formed.

$\left(D\right)$:-If there were two conducting shells with charge at their common center, then the $E$ will vanish twice , But since shells are thin, there will just be two points of discontinuity where $E$ will go to zero and again catches up with the curve.

Hence, answer is option-(A).