Two long thin conducting tubes are concentric with each other. The outer tube has a radius R and has a current I while the inner tube has a radius R/4. To cancel the field at points r > R, the inner tube must have a current
a.) running parallel to I of magnitude I/4
b.) running parallel to I of magnitude I
c.) running antiparallel to I of magnitude 1/4
d.) running antiparallel to I of magnitude I
Acc to ampere circutal law intgration of B.dl = mu naught * I. This I is the I surrounded by the path chosen for the line integral of B. To cancel B field the current should be of ...