Magnetic field between two parallel wires

[fishingspree2]

Homework Statement

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

Homework 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?

 

[JaWiB]

Maybe you are not taking into account that the magnetic field is due to the current of _two_ wires

 

[Senjai]

Note that the forces on these two wires will attract each other, combining together and forming double the magnetic field because the fields are in the same direction :)

 

[Fazza3_uae]

I think that it is correct for anti-parallel case. 30 A for each wire.

 

[engrshari]

you have to consider currents for both wires. so in this case current will b 2i.