Question

Consider the current-carrying wires in the figure.

Both cases consist of long straight wires carrying a current I.

In both cases, the wire is also bent in the shape of a circular loop of radius R.

The only difference is in how the bending of the wire is done to create the loop.

We are interested in the magnitude of the net magnetic field at the center of the loop.

If BA and BB are the magnitudes of the net magnetic fields at the center of each loop respectively, then which of the following statements is true?
1)BA < BB
2)BA = BB
3)BA > BB
4)There is not enough information to compare BA and BB

Answer 1

I don't see the figure, so I don't know which loop might have more turns. If they are both one-turn loops with the same current and the same loop radius, then the B fields at the center are the same.

But, how can you make a circular loop if (as you say) the wire is straight?

Answer 2

I'll tell you the answer on Tuesday.

Answer 3

you forgot to take into account the field created by the long straight ends of the wire

yes the loops have current flowing in opposite direction so the field is in opposite direction

but in one situation, the field is additive with that created by the straight end of the wire, and in the other situation it subtracts from the other

if both wires current to the right
then they exert B in

the loop if current is counter clockwise makes B out, at the center

loop if current clockwise makes B in at the center

so the wire with clockwise has a higher B than the wire with counter clockwise