Question

Charges are placed at the vertices of a square as shown in the diagram. If charges at $A$ and $B$ are interchanged with $C$ and $D$ respectively, then,

• A. Only magnitude of electric field will change at the centre
• B. Both magnitude and direction of electric field will change at the centre
• C. Only direction of electric field at centre will change
• D. Both magnitude and direction of electric field will remain unchanged

Answer 1

Answer: (C)

Electric field $E$ due to a single charge $Q$ is given by
$E=\left(\frac{1}{4{\left(\pi \epsilon \right)}_0}\right)\frac{Q}{r^2}$
Net electric field $E_{net}$ due to all the charges at the centre O is shown by in the following figure.

We can see that on interchanging the charges at $A$ and $B$ with charges $C$ and $D$ , there is no change on the magnitude, but its direction changes.