00:01
Okay, in this problem we have a length of wire.
00:03
The length of this wire is 13 .0 meters.
00:08
Coiled up 70 times, so there are 70 turns in the coil.
00:14
And it's parallel to a magnetic field equal to 0 .19 tesla.
00:21
And we want to find the flux through this coil.
00:24
So the first thing we want to do is find the radius of the circle that the coils make, that the coil makes.
00:34
So we have our coil here and the wires wrapped around.
00:38
So we have many different turns.
00:43
So the radius is just going to be from the center out to the edge.
00:49
So what we can do here is say the circumference of a circle is 2 pi times r.
00:55
But in this case, we also have this long wire that's been coiled up 70 times.
01:02
So each circle has the total length l, or has a circumference of a total length l divided by the number of turns, n.
01:16
So 2 pi r in this case is equal to the length of the wire divided by n.
01:21
So we can solve for the radius here by dividing by 2 pi.
01:26
So we have l over 2 pi n is the radius.
01:32
And ultimately, we want to find the area...