• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Copper wire resistance

A copper pipe has an inside diameter of 6.720 cm and an outside diameter of 8.000 cm. What length of this copper pipe will have a resistance of 8.05 × 10-3 W?

so i am using the equation R=rho(L/A)

A=pi(d2-d1)^2/4 which is 1.29E-4 m

and for copper rho is 1.7E-8

so 8.05E-3=(1.7E-8)(L/1.29E-4)

then L=60.93 m

but this isnt right.

please help me where i am going wrong.
 

Dick

Science Advisor
Homework Helper
26,258
618
Where did you get the funny area formula? Don't you want pi*r2^2-pi*r1^2 where r's are the radii?
 
well i was just going to use the diameter...but i recalcualted te area using the radius instead and i came up with the same value
 

Dick

Science Advisor
Homework Helper
26,258
618
But (d2-d1)^2 is not equal to d2^2-d1^2.
 
so what did you get for the area...i still get 1.29E-4 m
 

Dick

Science Advisor
Homework Helper
26,258
618
0.00147 m^2. Throw out that formula and subtract the area of the two circles!!!!!
 
ok ok....i will do that
 

Related Threads for: Copper wire resistance

  • Posted
Replies
1
Views
4K
  • Posted
Replies
5
Views
2K
  • Posted
Replies
4
Views
182
  • Posted
Replies
6
Views
2K
  • Posted
Replies
1
Views
2K
  • Posted
Replies
12
Views
2K
  • Posted
Replies
2
Views
30K
Replies
1
Views
2K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top