Electric Charges and Fields - Result Question 1

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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]

======= ####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]

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/electric-charges-and-fields/electric-charges-and-fields—result-question-1.md (a) $F$

(b) $\frac{9 F}{16}$

(c) $\frac{16 F}{9}$

(d) $\frac{4 F}{3}$

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Solution:

  1. (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 $q_B=-Q+\frac{Q}{4}=\frac{-3 Q}{4}$

$F_1=\frac{kq_A q_B}{r^{2}}$

$\Rightarrow F_1=\frac{k(\frac{3 Q}{4})^{2}}{r^{2}}=\frac{9}{16} \frac{kQ}{r^{2}}=\frac{9 F}{16}$