00:01
So, to work out the total resistance, we can first work out the parallel resistance.
00:07
That is equal to 1 over 90 plus 1 over 80.
00:20
This is equal to 17 divided by 720.
00:27
Taking the reciprocal resistance of the parallel section is equal to 720 divided by 17 oms.
00:42
So the total resistance is the extra 20 oms resistor plus the resistance of the parallel sections.
00:57
That's 720 divided by 17 oms.
01:04
And this gives 62 .3529 arms, rounding it up to one significant figure, 62 .4.
01:31
Now for question or part b, we know arms law which is v equals i r.
01:55
So we can rearrange for i.
02:05
Substitute the numbers in 12 volts divided by our current found in part a, 62 .3529 oms.
02:27
This gives a current of 0 .192 abs.
02:42
For part c, we can work out of the voltage first for the 20 -on resistor, subscript 20...