00:01
To find the magnetic field of a long current carrying wire, you use amper's law.
00:08
This law relates the magnetic field along the circumference of a circle defined by a distance from the wire.
00:18
Relates that magnetic field to the current through the formula, b equals mu not i over 2 pi r.
00:26
So recognize that the circumference of the circle your distance is down in the denominator.
00:35
The mu knot is a fundamental electrical constant called the permeability of free space.
00:43
And it is 4 pi times 10 to the minus 7 tesla times meters over amps.
00:51
So no choice in that.
00:54
So here we're going to have a current of 3 amps, and we are at a distance of 0 .35 meters from the wire, and we want to determine the strength of the field, which is what that formula gives us.
01:14
So we'll put in the mu not, and the current will multiply it to 3, and divide by 2 pi, and then divide by the radius of the 2 .5.
01:37
The circle or the distance from the wire.
01:43
And notice that the 2 pi will cancel with some of the 4 pi...