(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Calculate the magnitude of the magnetic field at a point midway between two long, parallel wires thar are 1.0 m apart and have currents of 10.0 A and 20.0 A, respectively, if the currents are:

a) In opposite directions and

b) in the same direction

2. Relevant equations

B=kI/(2 pi X r)

B is the magnetic field

k is the proportionality constant... 4pi X 10^-7

and r is the radius

3. The attempt at a solution

When it said that the currents move in opposite directions, i thought that the magnetic field at a point is B(net)= B(2) - B(1), and i got 4.0 X 10^-6 T. When it said that the currents move in the same direction, i did B(net)= B(2) + B(1), and i ended up getting 1.2 X 10^-5 T. But the answer at the back of the book is the opposite, the answer that i got for a turns out to be the answer for b and vice versa... are my equations wrong?

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# Homework Help: Ampere's Law of wire

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