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Investigating the factors affecting the resistance of wire

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Investigating the factors affecting the resistance of wire

In this experiment I will be investigating if the length of wire affects the resistance


The longer the wire the higher the resistance

Scientific knowledge

The free electrons in the wire leave the atoms and flow through the wire. The atoms therefore become positive ions.

   The resistance will increase when the length of the wire increases because the electrons travelling through the wire in random directions colliding with other electrons and ions in the wire. If the wire is longer the electrons will collide with more ions transferring kinetic energy to the ions in the wire causing the ions to vibrate more vigorously generating heat. So the electrons transfer kinetic energy slowing them down causing the voltage (bigger difference in energy) to increase. The voltage is a measure of the energy transferred by one coulomb of charge between two points in a circuit. V = E/Q. V being the voltage, E the energy and Q the charge.

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Same temperature-This alters the results (room temperature)

Same current-This alters the results


  1. Set up the circuit
  2. Attach the constantan wire to the meter ruler  
  3. Clip one crocodile clip on 0cm and one on 100cm
  4. Turn the dial on the P.S.U. until the reading shows 1 amp on the ammeter
  5. Measure and record the reading on the voltmeter
  6. Repeat this reducing the distance by 20 cm each time until the distance  is 20 cm
  7. Repeat steps 1-6 twice more for repeat readings
  8. Calculate the resistance using R=V/I

Range of Values

I am using 20cm – 100cm of constantan wire

Preliminary Work

I carried out the experiment to determine the

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Our procedure was good we worked in a systematic way starting from 20 cm working our way up to 100 cm and then repeating our experiment three times. Our evidence was good as well with only one anomaly which we repeated to give a more precise result. I think we had an anomaly because it is extremely difficult get the current 1 amp on the ammeter and when we read the ammeter the current could have changed. The results are reliable because the averages are all close together proving that they are not anomalies. We could improve the experiment by being more accurate on the wire by attaching a thin wire to each crocodile clip reducing the area touching the crocodile clip so our measurements would be more accurate. The results are compatible with the conclusion because they matched up even with anomalies. To do further research I would get five different thickness of wire set up the circuit as before. But change the thickness instead of the length and keep the length the same and measure the voltage.

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