00:01
Okay, we have a region with area a that has a magnetic field.
00:06
I'm drawing it pointing into the board, but it could be either way.
00:11
We don't really matter for this problem because we're not asked the direction of the induced emf.
00:18
So we're asked to find the emf after time t.
00:23
We know that b equals zero for t less than zero.
00:29
That actually doesn't really affect us much.
00:32
We're really just saying, all right, let's figure out what's going on for t greater than zero.
00:37
For t less than zero, there's no induced emf.
00:40
So there suddenly will be one when the magnetic field starts to switch off.
00:47
So we know from faraday's law that the emf that's generated around that loop there is minus deflux dt, where the phi is the flux of magnetic field...