# Pretty easy ENGE question

Pretty easy Circuit question...

So, im in my first year ENGE Class second week in, and im given this diagram

## Homework Statement

Basically Im given this Diagram (attachment)

And told to find the total Resistivity if using AWG 18

So, i got

P=800W
E=100V
R=E^2/P = 15.125 Ohms

## Homework Equations

So for the Resistivity R = p l/a.

## The Attempt at a Solution

But im completly unsure how to get p l & a.

This isn't even a assignment question it was a example done in class on the board, but my instructor just randomly says everything and doesnt explain anything.

So when alls said and done I have

R = 4.13
I = 110/23.5= 4.7 Amps

But absolutly no clue as to how to get it :(

#### Attachments

• untitled.JPG
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So,
p = resistivity of copper = 10.37 CM
l = length of wire = 200m / 0.3048 = 656.17 ft
a = area of 18 AWG = 1624 CM

R = 10.37 * 656.17 / 1624 = 4.18

So then to get I i got

I = E / R
I = E / R1 + R2 + R3
I = 110V / 4.18 + 4.18 + 15.125
I = 110/23.485
I = 4.68

Is there any way i could have done this without having to convert the meters to feet?

cm is a unit of length
CM is circular mil

you said they should all be in my text. Everything in my text is based off CM, i dont know why but it is >_<

A circular mil(or CM) is diameter is mills squared

OR

1 mil = 0.001 in.

That's what my book says....

Your resistivity(or rowe) should be in Ohms * CM / ft.

yah that sounds right, i just dont know how to make symbols on here so well... i didnt @[email protected]

Astronuc
Staff Emeritus