00:01
Okay, so for this question we've got a loop of wire that carries a current of 0 .2 amperes.
00:07
So we say current, which is denoted by i, 0 .2 amperes.
00:19
The radius of the loop, 0 .09 metres.
00:24
Calculate the magnitude of the magnetic field at a distance, which we'll just call z, is 0 .42 metres down the coil, along the axis of the coil, from the centre of the loop.
00:43
And b is equal to question mark how many teslas.
00:47
Okay, and then for part b we'll move on to that in a little bit.
00:52
So let's just do part a first.
00:55
And what we need to use here is ampere's law.
00:59
And we have a formula using ampere's law for the magnetic field of a current loop.
01:06
So we know that b is equal to mu naught, permeability of free space, which is also 4 pi times 10 to the minus 7 teslametres over amperes, but we'll get to that in a second, times current times r squared, which is the radius of the loop, divided by 2 times r squared plus z squared to the power 3 over 2.
01:47
Now your r squared is the radius of the loop, the z is the location along the axis of the loop that we're using.
01:54
Okay, so this is the equation that we need...