Magnetic force between 3 straight wires

1. Apr 5, 2004

kiewelb

Find I2 so that the magnetic force per unit length on each wire is zero. The three parallel wires are equally spaced. Current directions are shown with '<' or '>'.

I1 = I3 = 1 A

< I1 < I1 < I1
---------------
> I2 > I2 > I2
---------------
< I3 < I3 < I3
---------------

I have the formula F = (mu0*I*I')/(2*pi*r) with mu0 = 4*pi*10^-7 but have no clue where to take this to figure out I2 with the 3 wires.

Sorry if this is really easy but I'm not too quick with Physics. Thanks for any help.

2. Apr 6, 2004

gnome

r in the formula is the distance between 2 wires. So let r = distance between wire 1 and wire 2. Then the distance between wire 1 and wire 3 is ______?

Next, use that formula to find the force exerted on wire 1 by wire 2, and the force exerted on wire 1 by wire 3. If the NET force on wire 1 is 0, those two forces must be equal in magnitude & opposite in direction so set the two F's equal to each other & solve for I2.

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