00:01
Okay, we have this electric circuit.
00:03
The resistor values have been written in, and the battery voltages are over here.
00:12
And we've actually drawn in directions for our currents.
00:18
We want to solve the circuit, find all three currents.
00:24
Okay, so first of all, we'll use the junction rule.
00:28
It tells us that i -1 is i -2 plus i -3.
00:32
Just look at the junction up at the top.
00:34
We got i1 coming in i2 and i3 coming out then i'm going to label my loops the left -hand loop i'll call number one the right -hand loop is number two and i'll write down the loop equations there's loop one i'm just using the usual rules for writing out loop equations um over there in just a moment so the way it works is i'm going to walk around the loop in the direction of the arrow.
01:37
If i hit a battery and i'm going from minus to plus, i add it.
01:42
If i hit a battery and i'm going minus to plus, i subtract it.
01:47
Excuse me, plus to minus.
01:48
I subtract it.
01:49
So i add if i'm going minus to plus.
01:52
I subtract if i'm going plus to minus.
01:55
When i hit a resistor, if i'm going with the current, i subtract the current.
02:01
Times the resistance.
02:03
If i'm going opposite the current, i add the current times the resistance.
02:10
And i do that going around both loops...