00:01
All right, we're looking at question 28 .52, and here we have a solenoid that's a toroid.
00:07
So the formula that we want to use to calculate the magnetic field is normally this one up here, the top one.
00:15
But since we're told the relative permeability of the core, we're going to want to use this expression instead, where we're replacing this mu not with km times mu not, where km is this relative permeability.
00:32
So we have, let's take a look at the information that we're given here.
00:39
We have the number of turns.
00:41
We have the radius, which i'm just going to convert to meters here before we do anything.
00:47
So it'll be easy to plug in.
00:49
We're given the current and we're given this relative permeability.
00:53
So all we really need to do here is just plug in all these numbers that we have.
00:59
So we have km, the permeability of free space, and the current, and then divided by 2 pi r.
01:09
And r is going to be our 0 .06 here.
01:12
So when we plug this all in, we should get that b is equal to 0 .267 tesla.
01:24
That's the answer to part a.
01:26
Now part b asks the amount due to atomic currents...