00:01
Okay, so you're talking about equivalent resistances, where you were told that the resistance through resistor 1 is 11 oms, through resistor 2 is 10 oms, and through resistor 3 is 47 oms.
00:21
So if you look at circuit number 1, circuit number 1, they are all in series.
00:27
Since they are all in series, you add all of the resistances together.
00:39
And this gives you 68 oms.
00:46
For resistor 2, you are talking about, sorry, for a circuit 2.
00:52
All three of those resistors are in what we call parallel.
00:59
So resistors in parallel have a formula 1 over req, which is 1 over the equivalent resistance, is equal to 1 over r1 plus 1 over r2 plus 1 over r3.
01:41
You may have seen this formula slightly differently.
01:45
If you're just talking about two resistors, they will create.
01:49
Common denominators and cross -multiply but this is where this comes from so one over r1 is one over 11 plus one over 10 plus one over 47 and to get the equivalent resistance this whole thing is to the negative one power because remember one over req is the same as req to the negative 1 power using your exponent loss.
02:24
So you can make your calculator do this, or you could make common denominators and do this yourself.
02:32
So 1 over 11 plus 1 over 10 plus 1 over 47, and you want to take that answer and raise it to the negative 1.
02:57
One power and then we usually still want it as a fraction.
03:10
So, or they have rounded it, okay, so we can round this to 4 .71 oms...