Q.
        The figure shows a closely wound coil on a square core of inside edge length $l$. The no. of turns per unit length of the coil is $n$. Each turn carries current $i$ into the plane of paper and out of the plane of papers. ABCD is an
Amperian loop enclosing an open surface in the plane of the paper. The current enclosed by the loop is
      
          Moving Charges and Magnetism
          
        
      Solution: