A copper wire and an iron wire - Potential difference

  • Thread starter mk9898
  • Start date
  • #1
109
9

Homework Statement


A copper wire and an iron wire of equal length l and diameter d are joined, and a potential difference V is applied between the ends of the composite wire. Calculate the potential difference (in volts) across the iron wire. Assume that l = 2.00 m., d = 0.30 mm., and V = 156 V.

The Attempt at a Solution



156 * 10 / (10+1.7) = 133.33 volts

156 * 1.7 / (10+1.7) = 22.67 volts

My question is: where do these equations come from? What are the derivations?

Thanks in advance.
 

Answers and Replies

  • #2
How did you come up with with your solution attempt and what are your thoughts behind it ?
 
  • #3
109
9
I should have noted that the solution and question in and of itself I found while searching google. I just want to know how they came about this solution i.e. where did this equation come from.
 
  • #4
Ah... I think its a remix of Ohm law, V=RI , where they have rewritten the resistance as L/(σ*A) , where σ is the conductivity of a given material.

I not entirely sure tho, some units on the calculations would have helped a lot hehe
 
  • #5
109
9
I not entirely sure tho, some units on the calculations would have helped a lot hehe
Yea exactly what I thought. In general it is: ##\Delta V_1 = \frac{\Delta V * R_1}{R_1+R_2}##. I tried to work backwards having the denominator on the other side but still not sure what it could be. I then thought it has something to do with resistors in parallel but this exercise comes from a chapter before DC circuits are introduced.
 
  • #6
On the right track , try to Calculate Rcopper and RIron and the current separately.
I think you are supposed to find the conductivity of Iron and copper in your book as they are not stated in the problem.
 

Related Threads on A copper wire and an iron wire - Potential difference

  • Last Post
Replies
3
Views
10K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
1
Views
6K
Replies
2
Views
27K
  • Last Post
Replies
6
Views
14K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
4
Views
307
  • Last Post
Replies
2
Views
5K
Replies
2
Views
8K
Top