Question

4 2

The magnetic field at point 1 is 18 mT as shown in (Figure 1) . Assume that the wires overlap closely and that points 1 to 4 are equally distant from the wires adjacent to them. Lastly, assume that any wires not immediately adjacent to a point, do not affect the magnetic field at that point. What is the magnetic field strength at points 2, 3 and 4 in (Figure 1) ?

Answer 1

The B on a wire is constant. So if this was a straight wire, B would be 18 everywhere. The key point here is that the wire wrapsareund.

So at point \(2,\) we have \(18 \mathrm{mT}\) on the top wire, and another \(18 \mathrm{mT}\) on the bottom wire. Since it's going in the same direction (both I's are positive), you add them to get \(36 \mathrm{mT}\).

At point 3 you have \(18 \mathrm{mT}\) on the top wire, and \(-18 \mathrm{mT}\) on the bottom wire (it's going the other direction, so I is negative). We add them together to get \(0 \mathrm{mT}\).

At point 4 again, both wires have \(18 \mathrm{mT},\) but since the point is in between and they're going opposite directions, both \(\mathrm{Bs}\) are positive and you add them to get \(36 \mathrm{mT}\).