00:01
So in this problem, we're told that i is equal to v over r, and that's what we're going to use to answer both parts of the question.
00:10
And so first we're asked to find d -i, dr when r is equal to 6, and v is a constant with the value of 24.
00:18
So we can rewrite our equation here and write that i is equal to 24 over r, because we know that the v is that the v.
00:31
Is not changing and now we can take the derivative with respect to r so d i dr is going to be equal to actually might be easier to write this also it's also equivalent be easier to write it as 24 r to the negative first just so we can easily apply the chain rule and so when we apply the chain rule we multiply by the exponent and subtract 1 so we get negative 24 r times r to the negative second.
01:16
And now we can plug in six, because we're told that r is equal to six.
01:23
And we get negative 24 over 6 squared, which is negative 24 over 36.
01:43
We can divide by 6 and get negative negative, actually we can even divide by 12, and we can get negative 2 over 3.
01:58
And that's our answer for part 1.
02:00
And for part 2, we're instead told that i is a constant with the value of 4.
02:06
And again, we have to find, actually in this case we're finding dvdr, so the derivative with respect to r of the voltage...