Help with magnetic fields (HSC) (1 Viewer)

[jeffwu95]

I drew the magnetic fields around the wires and determined it to be B but the answers says A

 

[SpiralFlex]

First of all you need to notice that these two rods with current passing through each will generate a magnetic field in the form of coeccentric rings/circles.

So we need to determine the direction of the magnetic field in each wire and consider the net effect. In each wire, we can use to right hand grip rule, thumb points into the page and your fingers wrap naturally around in a clockwise manner. Hence the direction of the magnetic field is clockwise in each. Hence the summed up effect is clockwise. The point A, take a tangent to the ring - it is A.

 

[jeffwu95]

yup yup