 Now, we can look at the magnetic field at the center of a loop of wire, which is carrying a current. Here's the equation we're going to be working at for this one. Again, this comes from the integration of the biosavart law, but we're not going to show you the detailed integration of it. The mu naught up here on top is our magnetic constant. The I is our current. The R is the radius of our loop. And N is the number of loops. Sometimes you'll see this equation without the N, which means they assume it's just a single loop of wire forming a circle. So if I've got a loop of wire over here, this equation actually only finds the magnetic field at the center of that loop. It doesn't give me the magnetic field for any other position around that loop. And of course, that radius is then defined from that point in the center out towards the edge of where the wire is.