00:01
We are given a circuit that has actually three unknown quantities.
00:04
It has a current and a resistance we don't know and a battery.
00:09
First of all we want to write down the junction and loop equations.
00:15
So our junction equation, just think about that bottom junction.
00:22
We got i coming into it and also 1 amp and 6 coming out.
00:29
Then left hand loop is loop number 1.
00:34
Its equation looks like this.
00:50
Then the right hand loop is loop number 2.
01:00
Its equation looks like this.
01:36
Then we can use the junction rule equation to solve for the unknown current i which comes out to be 5 amps.
01:46
We can use loop 1 equation then to solve for r which tells us that r is 18 plus 2 divided by i which was 5.
02:15
That comes out to be 4 ohms.
02:20
Then we can use this equation to solve for e which comes out to be negative actually...