Question

Two concentric conducting thin spherical shells $A$ and $B$ having radii $r_{A}$ and $r_{B}\left(r_{B} > r_{A}\right)$ are charged to $Q_{A}$ and $Q_{B}\left(\left|Q_{B}\right| > \left|Q_{A}\right|\right)$. The electrical field along a line (passing through the centre) is

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

The electric field inside the shell $A$ is zero.

At the surface of shell $A, E_{A}=\frac{k Q_{A}}{r_{A}^{2}}$
Between the shell $A$ and $B$, at a distance $x$ from the common centre,
$E=\frac{k \cdot Q_{A}}{x^{2}}$ towards right, hence positive At the surface of shell $B, E_{B}=\frac{k \cdot Q_{A}}{r_{B}^{2}}$ towards right hence positive.
Outside both the shells, at a distance $x$ from the common centre, $E_{\text {out }}=\frac{k\left(Q_{A}-Q_{B}\right)}{x^{\prime 2}}$, towards left,