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The aim of this investigation is to find out if length will affect the resistance of a wire in an electrical circuit.

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Physics Sc1


The aim of this investigation is to find out if length will affect the resistance of a wire in an electrical circuit. Hopefully my research will be proven by the experiment.

Preliminary work

From research I discovered that resistance occurs when the charge carrying particles, called electrons travel along the wire and collide with atoms or other electrons in the wire. This causes resistance so the molecular structure of the wire determines the number of collisions, therefore level of resistance. I also found out in my research that if the wire is heated the resistance will increase. If the wire length decreases the resistance will also decrease. This is because the electrons have less wire.

We made sure the experiment was safe and a fair test by switching off the current between readings to prevent overheating, which could increase the risk of burns, as well as make the results inaccurate.

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Increase voltage noting ammeter reading and observing wire.Repeat above


As the current increases the wire gets hotter until it melts.


There is a heating effect. Fuses work by melting if the current is too great.


From my research I can predict that if I increase the length the resistance will increase, this is because the length and resistance are directly proportional. If I increase the length by 10cm the resistance will increase by about 0.5Ω.

If I double the length the resistance should double and if the voltage doubles the current should double as well.


  • Ammeter.
  • Voltmeter.
  • Crocodile clips.
  • Metre ruler.
  • Power pack
  • Wires.
  • Wire




  1. Set up equipment, as shown in the diagram.
  2. Use metre ruler to measure 50cm of wire, and attach the crocodile clips.
  3. Switch on power pack, use variable resistor to get 1v on voltmeter.
  4. Take reading from the ammeter, and then switch the power pack off to let the wire cool down.
  5. Repeat step 4 for lengths 60cm, 70cm and 80cm.


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The experiment sort of, followed Ohm’s Law. It didn’t quite follow Ohm’s Law exactly because Ohm’s Law is only correct if the temperature stays the same.

Most of the points plotted on my graph are close to the line of best fit.  This means the experiment was carried out well.

I have one anomalous result; the other results are very close to the line of best fit on the graph so must be quite accurate. The reason I have this anomalous results is due to change in temperature while completing the experiment.

I believe that I have gathered enough evidence to support my conclusion; I repeated the experiment three times for each different length to make sure and get an accurate average resistance.


  • I could have kept the temperature constant, and made sure of this, by keeping the length of wire in a water bath at a constant temperature.





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