How do I find the total Resistivity if using AWG 18?

  • Thread starter JeeebeZ
  • Start date
In summary, the conversation is about a circuit question involving finding the total resistivity using AWG 18. The participants discuss the steps they took to solve the problem, including finding the resistivity of copper, the length and area of the wire, and using the equation R = p l/a to find the total resistivity. They also mention converting between units and the use of different units in engineering.
  • #1
JeeebeZ
40
1
Pretty easy Circuit question...

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

Homework Statement


Basically I am 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 I am completely 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 doesn't 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 :(
 

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  • #3
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?
 
  • #5
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 don't know why but it is >_<
 
  • #6
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.
 
  • #7
yah that sounds right, i just don't know how to make symbols on here so well... i didnt @_@
 
  • #8
JeeebeZ said:
cm is a unit of length
CM is circular mil
Ah, my mistake. I should have recognized it, but its a unit I now use seldom. 1624 cmil is correct.

If resistivity is given in SI/metric units, one does not have to use feet. The problem in the US is that most engineering is still taught with English/British units, and there are sometimes mixed units.

I use both at work, but prefer metric.
 
  • #9
I agree...prefer metric to work problems with...but still understand english better, when someone yells out a distance or figure or something...
 

FAQ: How do I find the total Resistivity if using AWG 18?

What is ENGE?

ENGE stands for Engineering and refers to the application of scientific and mathematical principles to design, develop, and maintain structures, machines, devices, systems, and processes.

What makes an ENGE question "pretty easy"?

An ENGE question is considered "pretty easy" when it does not require a high level of technical knowledge or specialized skills to understand and answer. It may also involve basic concepts and principles that are commonly taught in introductory engineering courses.

Can non-engineers understand "pretty easy" ENGE questions?

Yes, "pretty easy" ENGE questions are designed to be understandable for individuals without a background in engineering. They may require some basic understanding of scientific and mathematical concepts, but they do not require specialized knowledge or training in engineering.

How can I improve my understanding of "pretty easy" ENGE questions?

To improve your understanding of "pretty easy" ENGE questions, you can review basic engineering principles and concepts, practice solving similar problems, and seek help from experts or online resources. It may also be helpful to approach the question logically and break it down into smaller, more manageable parts.

Are "pretty easy" ENGE questions important in the field of engineering?

Yes, "pretty easy" ENGE questions are important as they provide a foundation for understanding more complex engineering problems. They also help individuals develop critical thinking and problem-solving skills, which are essential in the field of engineering.

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