The magnetic induction on the equatorial line of a short magnet at distance d from the centre of the magnet is B. At what distance on the equatorial line of the magnet the magnetic induction would become 4B?

Explanation

To solve the problem, we need to determine the distance on the equatorial line of a short magnet where the magnetic induction becomes four times the initial value. Let's break down the solution step by step.

### Step 1: Understand the formula for magnetic induction
The magnetic induction \( B \) at a distance \( r \) from the center of a short magnet is given by the formula:
\[ B = \frac{\mu_0}{4\pi} \frac{m}{r^3} \]
where:
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