Electric Potential: Practice Problem & Solution
Four point charges $-Q$, $-q$, $2q$ and $2Q$ are placed, one at each corner of the square. The relation between $Q$ and $q$ for which the potential at the center of the square is zero is: (2012 Pre)
Solution Explained:
To solve this problem, we apply the core principles of Electric Potential. Understanding the underlying formula is key to arriving at the correct answer below:
The potential at the center is the scalar sum of potentials due to all four charges. Let the distance to the center be $r$. $V = \frac{k}{r}(-Q - q + 2q + 2Q) = \frac{k}{r}(Q + q)$. For $V = 0$, $Q + q = 0 \implies Q = -q$.
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