Question

A loop of irregular shape carrying current is located in a external magnetic field.if wire is flexible it will take shape of

1. Will remain in same shape

2. Circle

3. Square

4.None of these

Answer 1

You can think the answer in to the question in terms of force acting for each small segment in the given loop.
For the whole loop consider a given segment dl. Now the force on the segment of the loop is in the direction radial to the that segment. It has a tendency to move that segment of the loop in a radial direction. Now all the small segments around the loop will be also experience similar forces in the radial direction. Thereby all the segments will be pulled apart in radial direction. Therefore the coil continues to stretch itself as long as these forces are not balanced. This creates a circular shape of the loop.

Therefore option (2) is correct