Question

PLEASE HELP! I dont get this at all!!! :(
The resistance of a wire varies directly with its length and inversely with the square of its diameter .01 inch as a resistance of 10 ohms, what is the resistance of 60 feet of the same type of wire if its diameter is .02 inch?

Answer 1

The resistance of a wire varies directly with its length and inversely with the square of its diameter

means that

\[\Large r = \frac{kL}{d^2}\]

where r is the resistance, L is the length, d is the diameter, and k is some fixed number

Answer 2

Something seems missing though

Answer 3

in the problem something is missing?

Answer 4

can you post a screenshot of the problem?

Answer 5

yesss

Answer 6

ok thx

Answer 7

im about to send it, its #9

Answer 8

ok i see it now, thx

Answer 9

thank you!

Answer 10

it says that 100 ft of wire with a diameter of 0.01 inches has a resistance of 10 ohms

so all this means

L = 100, d = 0.01, and r = 10

plug all this in and solve for k

\[\Large r = \frac{kL}{d^2}\]

\[\Large 10 = \frac{k*100}{0.01^2}\]

\[\Large 10 = \frac{k*100}{0.0001}\]

\[\Large 10 = 1,000,000k\]

\[\Large \frac{10}{1,000,000} = k\]

\[\Large k = \frac{10}{1,000,000}\]

\[\Large k = \frac{1}{100,000}\]

\[\Large k = 0.00001\]

Answer 11

So

\[\Large r = \frac{kL}{d^2}\]

turns into

\[\Large r = \frac{0.00001L}{d^2}\]

Answer 12

Now plug in L = 60 and d = 0.02 and evaluate to find the final answer

Answer 13

\[\Large r = \frac{0.00001L}{d^2}\]

\[\Large r = \frac{0.00001*60}{0.02^2}\]

\[\Large r = ?\]

Answer 14

how did you get 1,000,000 as a denominator???

Answer 15

i divided both sides by 1,000,000

Answer 16

i got 1,000,000 from 100 divided by 0.0001

Answer 17

ohhhh okay got it

Answer 18

so what do you get for r

Answer 19

im doin it

Answer 20

ok

Answer 21

i got 15

Answer 22

that seems off, hold on

Answer 23

okay

Answer 24

I'm getting this

\[\Large r = \frac{0.00001L}{d^2}\]

\[\Large r = \frac{0.00001*60}{0.02^2}\]

\[\Large r = \frac{0.0006}{0.0004}\]

\[\Large r = 1.5\]

Answer 25

so you lost a zero somewhere, but other than that, it looks good

Answer 26

oops i only had 0.006 not 0.0006

Answer 27

ah that makes more sense

Answer 28

yeahh, my bad!
so is there anything i need to do for the problem???

Answer 29

yeahh, my bad!
so is there anything i need to do for the problem???

Answer 30

ohhh thats it

Answer 31

nope, you found the resistance of the 60 ft wire with a diameter of 0.02 inches so you're done

Answer 32

thank you sooo much !!!

Answer 33

yw