P. 4211. A current of I is flowing in a wire which is in the centre of an infinitely long straight metal tube. The radius of the tube is r the width of its wall is d (dr), and the young modulus of its material is E. By what amount does the radius of the tube change if a current of magnitude I is started in the tube which current is opposite to the current in the wire. Does the radius increase or decrease?
Deadline expired on 11 January 2010.