Point charge `q` and `-q` are located at the vertices of a square with diagonals `2l` as shown in Fig. Find the magnitude of the electric field strength at a point located symmetrically with respect to the vertices of the square at a distnace `x` from its centre.

Explanation

To find the magnitude of the electric field strength at a point located symmetrically with respect to the vertices of a square with charges \( q \) and \( -q \) at the vertices, we can follow these steps:

### Step 1: Understand the configuration
We have a square with vertices A, B, C, and D. The charges are placed as follows:
- Charge \( +q \) at vertex A
- Charge \( -q \) at vertex B
- Charge \( -q \) at vertex C
- Charge \( +q \) at vertex D
...