Electric Charges and Fields - Result Question 1
1. Two point charges $A$ and $B$, having charges $+Q$ and $-Q$ respectively, are placed at certain distance apart and force acting between them is F. If $25 %$ charge of $A$ is transferred to $B$, then force between the charges becomes: [2019]
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======= ####1. Two point charges $A$ and $B$, having charges $+Q$ and $-Q$ respectively, are placed at certain distance apart and force acting between them is F. If $25 %$ charge of $A$ is transferred to $B$, then force between the charges becomes: [2019]
c3eec34ec6b1fad69db54a20ad4b2dca40c2aa54 (a) $F$
(b) $\frac{9 F}{16}$
(c) $\frac{16 F}{9}$
(d) $\frac{4 F}{3}$
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Solution:
- (b) We know that,
$ F=\frac{kQ^{2}}{r^{2}}+Q \stackrel{A}{r} \xrightarrow{B}-Q $
If $25 %$ of charges of A transfer to B then
$q_A=Q-\frac{Q}{4}=\frac{3 Q}{4}$ and $q_B=-Q+\frac{Q}{4}=\frac{-3 Q}{4}$
$F_1=\frac{kq_A q_B}{r^{2}}$
$\Rightarrow F_1=\frac{k(\frac{3 Q}{4})^{2}}{r^{2}}=\frac{9}{16} \frac{kQ}{r^{2}}=\frac{9 F}{16}$
