13 April 2010

Magnetism

Problem 1.
Two long straight wires carrying the same current I and separated by a distance r exert a force F on each other. The current is increased to 4I and the separation is reduced to r/6 . What will be the force between two wires?
Solution:
The force (per unit length) between two parallel wires is
In the present problem the current is the same. Then
The current is increased to and the separation is reduced to then the force is