Four point charges $q_A = 2 \mu C$, $q_B = -5 \mu C$, $q_C = 2 \mu C$, and $q_D = -5 \mu C$ are loca

Question

Four point charges $q_A = 2 \mu C$, $q_B = -5 \mu C$, $q_C = 2 \mu C$, and $q_D = -5 \mu C$ are located at the corners of a square ABCD of side $10	ext{ cm}$. What is the force on a charge of $1 \mu C$ placed at the centre of the square?

Professor PC Thomas Classes · Answer

Due to the symmetry of the charge configuration, the forces from opposite corners are equal and opposite. The force due to $q_A$ cancels with $q_C$, and the force due to $q_B$ cancels with $q_D$. Thus, net force is zero.