Find the potential energy of a system of four particles placed at the vertices of a square of side l. Also obtain the potential at the centre of the square.

Explanation

To find the potential energy of a system of four particles placed at the vertices of a square of side length \( l \), we can follow these steps:

### Step 1: Understand the Configuration
We have four particles (charges) located at the vertices of a square. Let's denote the charges as \( q \) at each vertex.

### Step 2: Calculate the Work Done in Bringing the Charges
The potential energy of the system can be calculated by determining the work done to bring each charge from infinity to its position at the vertices of the square.

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