Question

Two wires are parallel to the z axis and are carrying currents of I1 = 5 A towards the +z direction and I2 = 25 A. Wire 1 is at (20,0) while wire 2 is at (0,0). Find the coordinates of the point where the net magnetic induction of the field due to the two wires is zero.

Answer 1

The only place where cancellation is possible is on the +x side of the 5A wire where the magnetic field from the 25A wire is cancelling the magnetic field of the 5A wire. Since the field is proportional to I/r, 25/x = 5/(x-.2m) Solving this gives x = 0.25m that is 5cm to the right of the 5A wire.

Answer 2

maybe it should be 25/(0.20m + x) = 5/x .. Am I right ?

Answer 3

Putting the magnetic field strength in terms of x, for the 25A wire, x is zero at the wire, giving a magnetic field that drops off as 1/r from x = 0, hence I thought 25/x. The field for the 5A wire drops off as 1/r from x = 0.2 hence 5/(x-0.2) [At x = 0.2 r = 0] Wire 1 is at x = 0.2 and wire 2 is at x = 0

Answer 4

ok thanks. :)