00:01
In this problem, we deal with a solenoid, which is a tightly wound coil of wire, generally in a cylinder shape that will have a particular length l and a particular diameter.
00:16
We'll call it little d.
00:17
Now, if we know the solenoid is much, much longer than its diameter, then we have an equation that pretty accurately describes the magnetic field throughout that, throughout that cellenoid.
00:33
So it's going to be a uniform magnetic field throughout the solenoid.
00:36
And the magnitude of that field is going to be given by the permittivity of free space, sorry, the permeability of free space, mu not, multiplied by the turn density.
00:46
So how many turns of wire we have per unit length, multiply by the current running through that coil, because of course we need a current to cause a magnetic field.
00:59
And just as a quick definition, right? this little n, like i said, is the number of turns, so big n divided by the length of this...