00:01
For this problem we have an rl circuit.
00:05
The resistance is 8 oms, the inductance is 2 .5 henrys, and the emf is 6 volts.
00:13
Our first task is to find the initial rate of change of the current.
00:18
So to do this, we want to call on our voltage loop law.
00:25
So we want to trace a loop around this circuit and account for each of the voltage.
00:32
Drops or gains.
00:35
So if we start with the emf, we're going to go up by the emf and then just going clockwise we're going to go down by the resistance so that voltage drop is ir and then down the inductance.
00:53
So that voltage is l times the change in current over the change in time.
00:59
And all of that gets us back to our initial point so that gives us zero.
01:05
Now initially when this first begins, there is no current.
01:11
The current is zero.
01:13
So we can disregard this second term at zero.
01:18
So this tells us that our emf is equal to l delta i, delta t, or our initial changing rate of that current is our emf over our inductance.
01:35
Now what is this? that is 6 volts divided by 2 .5 henry's and that gets us 2 .40 amps per second.
01:49
The second part we want to find the voltage drop across the inductance right after this begins...