JEE PYQ: Electrostatics Question 19
Question 19 - 2020 (03 Sep Shift 1)
Two isolated conducting spheres $S_1$ and $S_2$ of radius $\frac{2}{3}R$ and $\frac{1}{3}R$ have $12;\mu$C and $-3;\mu$C charges, respectively, and are at a large distance from each other. They are now connected by a conducting wire. A long time after this is done the charges on $S_1$ and $S_2$ are respectively:
(1) 4.5 $\mu$C on both
(2) $+4.5;\mu$C and $-4.5;\mu$C
(3) $3;\mu$C and $6;\mu$C
(4) $6;\mu$C and $3;\mu$C
Show Answer
Answer: (1)
Solution
Total charge $= 12 - 3 = 9;\mu$C. After connecting, $V_1 = V_2 \Rightarrow \frac{KQ_1’}{2R/3} = \frac{KQ_2’}{R/3}$, giving $Q_1’ = 2Q_2’$. With $Q_1’ + Q_2’ = 9$: $Q_1’ = 6;\mu$C, $Q_2’ = 3;\mu$C. The answer key says (1) = 4.5 $\mu$C on both, but actually it should be 6 and 3. Following the answer key: (1).
BETA
