It is requird to hold four equal point charges `+q` in equilibrium at the corners of a square. Find the point charge that will do this, if placed at the centre of the square.

Explanation

To solve the problem of holding four equal point charges \( +q \) in equilibrium at the corners of a square with a charge \( Q_0 \) placed at the center, we will follow these steps:

### Step 1: Understand the Configuration
We have four charges \( +q \) placed at the corners of a square. We need to find the charge \( Q_0 \) that should be placed at the center of the square to keep these charges in equilibrium.

### Step 2: Identify Forces Acting on One Charge
Consider one of the corner charges, say charge 1. It will experience repulsive forces due to the other three charges (charges 2, 3, and 4). The forces between these charges are given by Coulomb's law.

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