# Trying to determine copper wire's resistance

Discussion in 'Science' started by flemetakis1, Dec 14, 2018.

1. ### flemetakis1New commenter

Hi there, I have been trying to determine the resistance for a variety of wires in the prep room. I use the simple circuit with the power supply the ammeter and the voltmeter. I put crocodile clips at the edges of the wire and I have results for all of them but the copper. When I connect the coper wire to the circuit the ammeter and the voltmeter just become crazy, the voltmeter doesn't even show the voltage I apply with the power supply, imagine that it shows one decimal lower. What's going on with the copper wire?

2. ### gainlyStar commenter

I think the problem is copper has such a low resistance so the voltage will be very low and the current very high.

3. ### gainlyStar commenter

You really need a wire with a fairly high resistance, certainly significantly higher than the connecting wires, to obtain reasonable results.

4. ### dunnocksStar commenter

try a longer wire. or a thinner one. But be careful, it gets hot

5. ### blazerStar commenter

Try reducing the voltage

6. ### gainlyStar commenter

In a series circuit the voltage from the power supply is shared between the components in the ratio of their resistances. From what you say, the resistance of the copper wire is probably much less than that of the connecting wires so the copper wire is only getting a small share of the total voltage.

7. ### flemetakis1New commenter

geosci likes this.

9. ### flemetakis1New commenter

To be honest the nichrome and constantan wires were much thinner actually, so that was totally reasonable

10. ### gainlyStar commenter

Resitivity is a property of the material, nothing to do with the length or thickness. If the wires were thinner that would make the resistance higher still.

11. ### rich_hodgettsNew commenter

You could always try using a digital multimeter to measure these resistances - no separate power supply required. The issue you will have is as others have said - the resistance of the connecting leads and the contact resistance between them and the sample wire may well be more than than that of the sample!