00:01
In this question, we have two wires.
00:03
They are three millimeters apart and they each carry 10 amps of current.
00:07
We want to calculate what the magnetic field is 25 centimetres away in the plane of the wires at a point labeled p.
00:17
So what we can do is we can use the biosavirlo.
00:20
We know that this states that the magnetic field is equal to mu -0, which is a constant, i, the current, over, 2 pi r, which is the distance away from the wire.
00:38
So what we can do now is apply this to the two wires that we've got, so we know that the resultant magnetic field is going to equal b from the bottom wire minus b from the top wire as they are in opposite directions.
00:53
So we can equate this to mu -0 multiplied by the current, which is given us 10 amps, over 2 -p, 1 minus the distance from the bottom wire minus 1 over the distance from the top wire.
01:16
Now we know the distance from the bottom wire is 25 centimetres, so rb is 0 .25 meters...