00:01
So we want to solve for the values of r1, r2, and r3, and we can do this by setting up a system of equations, since we know what the currents through these, through the circuit is going to be when we close the switch at points a and b or keep it open.
00:18
So when we keep the switch open, we're told that we have a current of 1 milla amp running through.
00:25
So what we can do is we can see here that the current is only going to flow through this outside loop here, through r3, r2, and r1.
00:34
And these are all in series.
00:35
So the equivalent resistance is just going to be the sum of these individual resistances.
00:42
So i have r1 plus r2 plus r3.
00:45
It's going to be equal to the supply voltage, 6 volts, divided by the current, which is 1 millimet amp in this case.
00:53
This is going to give us an equivalent resistance of 6 kilo -ooms.
00:58
So we'll just label this as our first equation.
01:03
Now when we have s closed at a, so right here, we can see that we have r2 in parallel with each other and in series with r1 and r3.
01:17
So for our equivalent resistance, we're going to have r1 plus r3, and we'll find that the equivalent resistance of these two r2 resistors in parallel is going to be one half of r2...