Suppose that the radius of cross section of the wire used in the previons problem is r. Find the increase in the radius of the loop if the magnetic field is switched off. The young modulus of the material of the wire is Y.

Explanation

Wthe the magnetic field is swiched the tension increase . The lenth of wire .
` Y = (T/A) //(Deltal/L)`
` or AL = (TI)/(TA)= (iaB) //(Ypi r^(2)`
`2 pi xx Delta r = (iaB 2pi a )//(Y pi r^2 ) ` .