Magnetic field between two parallel wires

1. The problem statement, all variables and given/known data

Two parralel wires are 8 cm apart. The magnetic field halfway between them is 300 uT. What equal currents must be in the wires? Consider parralel and antiparralel currents

2. Relevant equations
I use Ia=Ib

B = (u*i) / (2*Pi*distance) where distance = 0.04 m (0.08m divided by two since it is halfway)

then I solve for I, I get 60 Amperes, the answers is 30 amperes

What to do?
 
279
0
Maybe you are not taking into account that the magnetic field is due to the current of _two_ wires
 
104
0
Note that the forces on these two wires will attract eachother, combining together and forming double the magnetic field because the fields are in the same direction :)
 
I think that it is correct for anti-parallel case. 30 A for each wire.
 
you have to consider currents for both wires. so in this case current will b 2i.
 

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