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Find the length of wire needed to have a resistance of 10 Ohms

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Introduction

        28/04/2007

Experiment to find the length of a piece of wire needed to create a resistance of 10 Ohms (Ω)

The aim of this investigation is to find the length of wire needed to have a resistance of 10 Ω.  

Electricity is the flow of electrons within a circuit. In current electricity negative charges are made. Resistance is anything that hinders movement. The definition of resistance is; ‘Property of an electrical conductor that limits how easily an electrical current flows through it. Measured in ohms (Ω).’

The resistance of the conductor is higher when the conductor is thinner and longer, the resistance is lower when the conductor is shorter or wider in diameter.

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This is because of the particles in the material of the wire/ conductor and how the material moves around them,

E.g.

Low Resistance

In the thicker wire the particles are a lot more spaced out so it is easier for the electric current to move around the particles- if the particles collide kinetic energy is transferred to the particles causing an increase in heat.  

High Resistance

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In the thinner wire the particles are a lot closer together so that the movement of the current is hindered.

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Middle

Prediction

I predict that the resistance will increase as the length of wire increases. The longer or  thinner the wire is, the higher the resistance. This is because in the thinner/ longer wire the particles are a lot closer together so that the movement of the current is hindered.

I will record my results on a graph and will look to see if my results are proportional. I predict that my graph will go in a steady relatively straight line . If there are any anomalous results I will know that my experiment has not been 100% accurate.    

Plan

I have chosen to investigate the increase in resistance against that of the wire so I can find how much is needed to produce a resistance if 10 Ω. It would also be too difficult to accurately measure the diameter of the piece if wire.  

I will set up a circuit like the one on the previous page, making sure that the power pack is set to 3 Volts, the voltmeter is in parallel to the circuit and the wire is securely fastened to the ruler using tape. This will ensure that the ruler is at its full potential length and to stop the wire from braking and or twisting.

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Conclusion

  • I used two different power packs as I did the experiment over two lessons, so it is possible that one of the power packs was not correctly set to 3V .
  • The temperature could have increased due to an accidental  increase in voltage, causing the particles in the wire to gain kinetic energy also causing an increase in temperature.
  • I may not have left enough wire to be attached to the crocodile clips when sticking to the metre rule, which could have resulted in an insufficient connection.
  •  The length of the wire could have had a twist in it/ it may not have been measured accurately.
  • It was not possible to accurately measure the diameter of the wire.
  • It is possible that I did not take the readings accurately as the ordinary volt/ammeters only give readings to 2 decimal places.

My results could have been more accurate if in would have had access to the following equipment;

  • A Digital voltmeter
  •  A Digital Ammeter

I could extend my investigation by taking more readings and plotting these results in more graphs and comparing these results to someone else’s.

Physics        Mr Wilson

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