# Resistance of Wire HeLp

1. Feb 7, 2008

### BuBbLeS01

Resistance of Wire....HeLp!!

1. The problem statement, all variables and given/known data
A 122-cm-long wire is made by welding a 0.36-mm-diameter, 21-cm-long copper wire to a 0.47-mm-diameter, 101-cm-long iron wire. What is the resistance of the composite wire?

2. Relevant equations

3. The attempt at a solution
How do I do this since it is made up of 2 different materials????

2. Feb 7, 2008

### BuBbLeS01

do I just find the resistance of each one and add them?

3. Feb 7, 2008

4. Feb 7, 2008

### BuBbLeS01

how do I know they are in series?

5. Feb 7, 2008

### mikecal1

Yea They are not clear on that point do they mean the wires were welded end to end to make a longer wire, OR as is the case sometimes, were the two wires used in parralel to make a thicker wire. I assume ened to end ie series as the person writing the problem would most likley have said welded at both ends if he/she meant paralell. So calculate resistance of each piece and simply add

6. Feb 7, 2008

### BuBbLeS01

oh ok....thank you!

7. Feb 7, 2008

### Ignea_unda

If you re-read you have a 21-cm wire and a 101-cm wire. Therefore the only way this problem can work would be to have them end to end to have a 122-cm wire.

So, yes, as has been said above, just calculate both the resistances and add them together.

8. Feb 7, 2008

### mikecal1

Great catch Ignea, my bad I read problem way too quick!! gets me killed every time