Electric field due to a uniformly charged thin spherical shell
(A) is directed outward, if q < 0
(B) at a point outside the shell is same as that of electric field due to point charge.
(C) is finite and same everywhere inside the shell.
(D) is zero everywhere inside the shell.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) and (D) only
Apply Gauss's law to a spherical Gaussian surface of radius r, concentric with the shell of radius R.
\( \displaystyle E \cdot 4\pi r^{2} = \frac{q_{\mathrm{enc}}}{\varepsilon_0} \)
(A) is directed outward, if q < 0 — Incorrect. For a negative charge the field points radially inward; it is outward only for q > 0.
(B) at a point outside the shell is same as that of electric field due to point charge. — Correct. For r > R the whole charge is enclosed, so \( E = \frac{q}{4\pi\varepsilon_0 r^{2}} \), as if all the charge were at the centre.
(C) is finite and same everywhere inside the shell. — Incorrect. Inside the shell the field is zero, not a finite value.
(D) is zero everywhere inside the shell. — Correct. For r < R the Gaussian surface encloses no charge, so E = 0 at every inside point.
NCERT (2026-27):
Field Due to a Uniformly Charged Thin Spherical Shell – “… The electric field is directed outward if \( q \gt 0 \) and inward if \( q \lt 0 \). This, however, is exactly the field produced by a charge \( q \) placed at the centre O. Thus for points outside the shell, the field due to a uniformly charged shell is as if the entire charge of the shell is concentrated at its centre.
… However, in this case, the Gaussian surface encloses no charge. Gauss’s law then gives
\( \displaystyle E \times 4\pi r^2 = 0 \)
i.e., \( E = 0 \quad (r \lt R) \qquad (1.35) \)
that is, the field due to a uniformly charged thin shell is zero at all points inside the shell.”