00:01
In this problem, we're going to talk about the electromotive force.
00:05
So consider that we have a generator that is rotating.
00:12
So let's say that we have a magnetic field and a generator.
00:21
I'm going to drive like this.
00:23
Actually, let me try it a little better.
00:31
This is a generator and it rotates around this x's here.
00:41
With an angular velocity omega.
00:46
So the electric motive, electromagnetic force, epsilon generated, is equal to minus the derivative of the magnetic flux with respect to time.
00:59
Where the magnetic flux is equal to b, this is the magnetic field, times the area of the generator, times the cosine of theta, and theta here is the angle between b vector b and the unit vector that is perpendicular to the surface of the generator.
01:28
And notice that in our case, epsilon, the electromotive force, is equal to b .a.
01:38
Times phi prime, i'm sorry, phi dot, this is the derivative of phi, times sine of phi.
01:47
And the derivative of phi is just the angular speed.
01:52
So this is b a sine theta times, i'm sorry, sine phi, i'm sorry, times the angular speed omega.
02:00
Okay, so the electro -motive force is proportional to omega...