The electrostatic potential at a point on the surface of a charged spherical conducting shell of radius 10 cm is 120 V. The electric potential at a distance of 5 cm from the centre of the shell is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 120 V
The point 5 cm from the centre lies inside the shell (radius 10 cm). The electric field inside a charged conducting shell is zero, so no work is done in moving a charge anywhere inside it, and the potential is constant throughout the interior, equal to its value on the surface.
\( V_{\mathrm{inside}} = V_{\mathrm{surface}} = 120\,\mathrm{V} \)
NCERT (2026-27):
Potential Due to a System of Charges – “… The electric field inside the shell is zero. This implies (Section 2.6) that potential is constant inside the shell (as no work is done in moving a charge inside the shell), and, therefore, equals its value at the surface, which is
\( \displaystyle V = \frac{1}{4\pi\varepsilon_0}\frac{q}{R} \qquad [2.19(b)] \)”