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Trying to determine copper wire's resistance

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

  1. flemetakis1

    flemetakis1 New 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. gainly

    gainly Star 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. gainly

    gainly Star commenter

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

    dunnocks Star commenter

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

    blazer Star commenter

    Try reducing the voltage
     
  6. gainly

    gainly Star 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. flemetakis1

    flemetakis1 New commenter

    Thanks for your answers guys, actually nichrome and constantan do the job perfectly. Actually I have already googled it and I haven't read anywhere about huge differences in resistance, so that's why I put the thread. Thanks again!
     
    geosci likes this.
  8. gainly

    gainly Star commenter

  9. flemetakis1

    flemetakis1 New commenter

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

    gainly Star 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_hodgetts

    rich_hodgetts New 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!
     

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