00:01
So we have a wire of 25 centimeters long and it's carrying a current, we'll just say in this direction, of 33 amps, which is very, very high.
00:12
And we're told that the force on this wire due to the presence of a magnetic field is 4 .12 newton.
00:19
So let's say we have a magnetic field somewhere else here.
00:22
We actually don't know the direction.
00:24
And so we want to calculate what's the minimum magnetic field strength here? well, the force on a wire, a current carrying wire, is like the current in the wire times the length of the wire as a vector cross product with the magnetic field.
00:39
And the length vector points in the same direction as the current.
00:42
So this would be like i, l, b, sine, theta.
00:47
And so the reason we can only calculate the minimum magnetic field strength is, you know, if we don't know this angle, then really all we can solve for is b times sine theta.
00:58
We can't know what theta is unless we know what the magnitude of the field strength is but you could be dealing with a magnetic field that is very very weak and just has a value of whatever b sine theta would come out to be or you could be dealing with a very strong magnetic field that has a very very small angle relative to the wire...