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An Investigation into the factors Which Affect The Resistance of Wire.

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Introduction

Emily Clark LVS

Physics Resistance Investigation

02/05/2007

An Investigation into the factors Which Affect The Resistance of Wire.

Planning

In this investigation I am going investigate who the length of a piece of wire affects its resistance.

Method

  • Set up the apparatus as in the diagram shown,
  • Measure onto the length of wire lengths at intervals of 100mm from 100mm to 1000mm,
  • Then set the crocodile clips at the correct distance. The distance must be measured from the inside of the crocodile clip,
  • Then turn the circuit on with a voltage of 12v being omitted from the battery pack,
  • Take readings from the ammeter and the voltmeter and record in a table of results,
  • Then repeat the measurements twice, so in total you will have three different readings for each length. To take the three readings I will use a variable resistor, this will enable me to change the current between each reading. This will not affect the resistance though because in work that we have done previously we have found that if the same resistor is used no mater what current is passed through it, it always has the same resistance, so in effect the variable resistor has no purpose except to make three repeat readings possible because other wise you could take three readings at the same time and of course they will be exactly the same because you have not even turned the circuit off.
  • After each reading turn the circuit off so as not to over heat it.
  • Repeat this whole experiment for each different length.

I have decided to use this method because it is safe, it gives me a good range of results and is reliable as is possible in a school laboratory.

Apparatus

  • 1 Battery pack
  • 1 Voltmeter
  • 1 Ammeter
  • 2 Crocodile clips
  • 1 Length of wire of at least 1m in length made of ……….
  • 4 Connecting wires made of …………..
  • 1 Variable resistor

Diagram


Fair Test

To make this investigation as fair as possible I am going to take the following precautions.

  • Turn off the circuit after each reading to prevent the circuit from overheating as we know that temperature has an affect on resistance
  • If the investigation takes place over more than one lesson try and use the same equipment because even if it appears the same they may differ. So try and complete this investigation in one lesson
  • We must, for ease of measurement and to try and keep everything the same secure the wire to the table or any other non-electrical conducting solid surface, this is to try and prevent the wire from bending as we do not know if this would affect the resistance.

Safe Test

To make this investigation as safe as possible I am going to take the following precautions.

  • The wire is going to get hot during the investigation so to prevent burns I will turn the circuit off between each reading.
  • The wire is going to be fairly light and sharp at both ends and because of this if and end is loose I the air people may not be able to see it easily so I will quickly secure it to a surface to protect people from possible injury, especially their eyes.
...read more.

Middle

900

1000

I have chosen to use this range results for many reasons:-

  • If the length of wire is shorter than 100mm the wire will burn out.
  • A length of 1000mm is sufficient for this investigation but if required at a later date if could be extended.
  • I think that three repeats is also sufficient for this investigation.

Prediction

I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length. My reasoning for this is that  with electricity, the property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure.

As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current.

...read more.

Conclusion


As well as making these modifications, I could also expand on my investigation by testing the same wire but different widths of that wire. I would do this if I had more time to complete it. I think the circuit and method used was quite suitable although I would make the modifications above to improve my results. If I did this experiment again I would defiantly use top quality equipment, I would probably control the temperature and use pointers instead of crocodile clips. After changing those few things, there is not really much difference to how I would do the experiment again.

...read more.

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