Question 24 of 311

A charge of $4\mu C$ is to be divided into two. The distance between the two divided charges is constant. The magnitude of the divided charges so that the force between them is maximum, will be:

A$1\mu C$ and $3\mu C$B$2\mu C$ and $2\mu C$C$0$ and $4\mu C$D$1.5\mu C$ and $2.5\mu C$

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Answer: (B) $2\mu C$ and $2\mu C$

If after division, one of the charge is $q$ the other charge will be $\left(4-q\right)$. The force between them can be written as,
$F=\dfrac{Kq\left(4-q\right)}{{d}^{2}}$
For the force between them to be maximum,
$\dfrac{dF}{dq}=0 \Rightarrow \dfrac{K}{{d}^{2}}\left[4-2q\right]=0$
$\Rightarrow q=2\mu C$