00:01
Okay, so we have a circuit and let's say that we knew the resistance for each part of the circuit.
00:05
Let's say r1 is equal to 200 ohms.
00:13
R2 we are given is 169 ohms.
00:19
And r3 we're going to say is 600 ohms.
00:25
So the first thing i want to keep in my head when i see a circuit like this especially is what type of circuit is it? this is a series circuit.
00:32
So a series circuit means that you add the resistors.
00:38
It will give you the total resistance for this circuit.
00:42
We're first going to figure out the current that's going through the circuit and then we can figure out what we're interested in.
00:47
I want to figure out what the voltage drop over this resistor r2 would be.
00:52
First we have to figure out the current.
00:53
Now the current is going to run through this entire circuit.
00:57
And it's going to be the same current as it goes through each one of these resistors because these are in series.
01:02
So all the resistors in series have the same current flowing through them.
01:08
All right.
01:08
Now our job is to find the current for now.
01:11
Once we find the current then we can use ohm's law.
01:14
So ohm's law says that even for complex circuits in general the potential is going to be equal to the current times the resistance.
01:26
I'm going to say, let's say vi is equal to i times r sub i.
01:32
That just means whichever resistor we're talking about.
01:34
Now the current, we're not going to worry about the resistors.
01:38
In fact, i'm going to use ohm's law to get the current by saying that the potential at the battery, which is equal to 12 volts, is going to be equal to i times r1 plus i times r2 plus i times r3.
01:59
So the current is going to be the same because it's series.
02:02
Each resistor is going to be different...