Question

Charge $6,12and24$ nano coulombs are placed on the corners of a square of side $10\sqrt{2}$ cm. The charge that must be placed at the fourth corner so that the potential at the centre of the square may be zero is

• A. $42nC$
• B. $36nC$
• C. $-42nC$
• D. $30nC$

Answer 1

The correct option is C $-42nC$

Potential due to charge particle=kq/r

Now, potential at centre $=\frac{k\left(6nc\right)}{10}+\frac{k\left(12\right)}{10}+\frac{k\left(24\right)}{10}+\frac{k\left(\upsilon \right)}{10}$

given $V=0$ (potential at centre )
$\Rightarrow 0=\frac{k\left(6nc\right)}{10}+\frac{k\left(12\right)}{10}+\frac{k\left(24\right)}{10}+\frac{k\left(\upsilon \right)}{10}$

$\Rightarrow \upsilon =-42nC$