A uniform magnetic field parallel to the plane of paper, exsisted in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by figure.
 
1.  

 


There are N cells in the circuit of figure. The emf and internal resistance of each cell is E and rrespectively. The points A and B in the circuit divide the curit into n and (N-n) cells. The current in the circuit is
1.  E/r