Q.

Two very long current carrying wires A and B carrying current I0 (along z-axis) are placed at (-a,0) and (a,0) as shown. Find the value of magnetic field at (0,a)

1 μ0I02πa  
2 μ0I02πa  
3 μ0I04πa  
4 μ0I022πa  

Ans.

(2)

For infinitely long wire B=μ0I02πr,  r=a2,  Bres=2B