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An Investigation Of How The Resistance Of A Wire Depends Upon Its Length.

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An Investigation Of How The Resistance Of A Wire Depends Upon Its Length.


My aim is to find out whether the resistance of a piece of wire changes if the length of the wires altered.

I am planning to link the wire up to a circuit that contains an Ammeter and a Voltammeter. I will then take the readings from both of them. With these results I will be able to find out the resistance.

From this experiment I will take note of the length of the wire, the voltage reading for each of the different lengths and the amp reading. From these last two readings, I will be able to work out the resistance of the wire by using the simple formula:

Resistance = Potential Difference/ Current

  (Ohms)                (Volts)            (Amps)

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                                                Variable Resistor (Rheostat)

Prelim Work

Before doing this experiment I did some preliminary work. I found a computer program called ‘Focus On Science’. In this program it is possible to do a simulation of the test, to see what the results might be. In this test I used copper wire instead of nichrome wire. Although it was not entirely accurate, it helped show how I would set up the equipment and gave me some experience.

According to ‘Keith Johnson’s Physics For You’, as the length of wire increases, the resistance increases. This is fairly straight forward, as obviously if the wire is longer, the electrons will have to travel further, therefore being more exposed to ions and electrons in the wire, slowing it down. This gives me the impression that our results may have some sort of correlation. As long as all the variables are kept constant where necessary, I believe that there will be a pattern between the results from the different lengths of wire. I am using a variable resistor in the circuit to make a safe and reliable test. This way the current cannot be altered (as long as the variable resistor is left alone).


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Fair Test

  • It is very important to get the wire exactly (or as close enough) the right length for each test to guarantee it is a fair experiment.
  • I can also help guarantee a fair test by not changing or altering any of the equipment used.
  • The results from the voltmeter and ammeter should be rounded up (or down) to the same number of significant figures.
  • Each test should be carried out twice to rule out anomalies, and then the average should be found from these two results.
  • It is important to use wire with the same diameter for each test.


  • It is important that water is kept away from the experiments because someone could get electrocuted, or the equipment could become damaged.
  • It is also important that no one is silly while doing this experiment because it would be easy for someone to get electrocuted, or fall over and hurt themselves.
  • The power should be turned off when it is not being used, to ensure the safety of yourself or others.
  • The power should also be turned off when the length of the wire is being altered or the equipment is being rearranged.

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