Question

Two long straight parallel wires separated by L2 = 8.16 cm carry currents of equal magnitude but heading in opposite directions. The wires are shown perpendicular to the plane of this page. Point P is L1 = 1.96 cm from wire 1 and the magnetic field at point P is 1.22 x 10−2 T directed in the −y-direction. Calculate the current in wire 1.


I've used the formula B = (miu*I)/(2pi*r).
I've used the formula on each wire and solved for I. But I got two different answers, and non of those is correct. Somewhere I am missing steps. Can someone help me please.

Answer 1

B adds from each wire.

Btotal=constant(1/(1.96E-2) + 1/(8.16-1.96)E-2 You are tiven Btotal, solve for the constant.
Now find the B from wire 1.

B1=constant(1/0.0196) now that you have B1

use you formula to find current I.