# B-field wires

1. Mar 23, 2004

### tandoorichicken

Two parallel wires repel each other with a force per length of 1.00*10^-3 N/m when spaced a distance of 2.50 cm apart. If one wire has a current of 100A, what is the current in the other wire?

Don't know where to start this one.

2. Mar 24, 2004

### Chen

Two equations. First, the magnetic field that a wire with current creates at a distance of $$r$$ from it is:
$$B = \frac{\mu _0I}{2\pi r}$$
Second, the magnetic force that operates on a wire with current inside a magnetic field is: (When the magnetic field is perpendicular to the direction of the current)
$$F_m = IBl$$
To find the force per length, just divide it by $$l$$.

Now can you solve it?

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