A straight wire of length l can slide on two parallel plastic rails kept in a horizontal plane with a separation d. The coefficient of friction between the wire and the rails is `mu`. If the wire carries a current I, what minimum magnetic field should exist in the space in order to slide the wire on the rails.

Explanation

To solve the problem, we need to find the minimum magnetic field \( B \) required to slide a straight wire of length \( l \) on two parallel rails with a coefficient of friction \( \mu \) while carrying a current \( I \).

### Step-by-Step Solution:

1. **Identify Forces Acting on the Wire:**
- The wire experiences a magnetic force due to the current flowing through it in the presence of a magnetic field. This force can be expressed as:
\[
F_{\text{magnetic}} = I \cdot l \cdot B \cdot \sin(\theta)
...