JEE MAIN - Physics (2020 - 6th September Evening Slot - No. 21)
Consider the force F on a charge 'q' due to a uniformly charged spherical shell of radius R carrying
charge Q distributed uniformly over it. Which one of the following statements is true for F, if 'q' is
placed at distance r from the centre of the shell?
$${1 \over {4\pi {\varepsilon _0}}}{{qQ} \over {{R^2}}} > F > 0$$ for r < R
$$F = {1 \over {4\pi {\varepsilon _0}}}{{qQ} \over {{r^2}}}$$ for r > R
$$F = {1 \over {4\pi {\varepsilon _0}}}{{qQ} \over {{r^2}}}$$ for all r
$$F = {1 \over {4\pi {\varepsilon _0}}}{{qQ} \over {{R^2}}}$$ for r < R
Explanation
_6th_September_Evening_Slot_en_21_1.png)
Inside the shell for r < R
E = 0
hence F = 0
Outside the shell
E = $${1 \over {4\pi {\varepsilon _0}}}{Q \over {{r^2}}}$$
hence F = $${1 \over {4\pi {\varepsilon _0}}}{{Qq} \over {{r^2}}}$$ for r > R
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