Four point charges, `+0.2muC, +0.2muC, -0.2muC and -0.2muC` are placed on vertices A, B, C and D, respectively of square ABCD of side a. Calculate the electric potential at the centre of the square.

Explanation

To calculate the electric potential at the center of the square formed by the four point charges, we can follow these steps:

### Step 1: Identify the Charges and Their Positions
We have four charges:
- Charge at vertex A: \( Q_1 = +0.2 \, \mu C \)
- Charge at vertex B: \( Q_2 = +0.2 \, \mu C \)
- Charge at vertex C: \( Q_3 = -0.2 \, \mu C \)
- Charge at vertex D: \( Q_4 = -0.2 \, \mu C \)
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