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Resistance of Wire

Extracts from this document...

Introduction

Physics coursework

Resistance of Wire

Aim

The aim of this investigation is to investigate the resistance of a wire by using one of the factors, which will have an affect on the resistance.

Variables

Resistance of wire can be affected by the following factors:

  • Length of wire
  • Make of wire
  • Diameter of wire
  • Temperature of wire

The variable in which I will change for my investigation will be the LENGTH of the wire.  I have chosen this variable to change, as it will be easy to measure and to do.

Background

Resistance is calculated with the following equation:

Resistance (in ohms) = Voltage (in volts) / Current (in amps)

As the electrons in an electric current move around a circuit, they bump into atoms in the wires.  Atoms of different elements hold up the electrons to different extents.  For example, electrons pass easily through copper wire, but much less easily through tungsten or nichrome wires.  We say that copper has a lower resistance than tungsten or nichrome.

Resistance is anything in the circuit which slows down the flow of electrons / currents.  It is a sort of constriction in the flow.  

The unit of resistance is the ohm (Ω) and the standard abbreviation for resistance is R.

The factors which affect the resistance of a wire are:

The lengths of the wire

The cross sectional area of the wire

The type of material

The temperature

If there was a long thin piece of wire and a short thick piece of wire, the long thin one will have a higher resistance compared to the short thick wire.

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Middle

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To get through, the visitors will have to go in and out of the people in the corridor, which will slow the visitors down.  Because of this, it will be harder to get through, meaning the resistance will be higher.  Therefore if the corridor was shorter, the visitors will then have less people to get pass, having a lower resistance and vice versa.

Safety Procedures

There will be some safety procedures to take into account when doing this experiment.  You must make sure that the voltage on the power pack is not too high (preferably 4volts or lower), or otherwise the wire will be burnt, causing a minor injury if touched.  Also, do not put any other equipment in the water except the wire you will be testing and the thermometer.

Make sure you will be careful when cutting the wires into length, as you may cut yourself or the wire may accidentally go into your eyes.

Method

  1. Gather all equipment and materials needed

  2. Get a beaker full of water and coil the right length wire around the thermometer

  3. Place the thermometer in the beaker of water

  4. Connect the power pack to the ammeter and to one end of the wire in the beaker of water

  5. Connect the ammeter to the other end of the wire forming a series circuit

  6. Now connect the voltmeter in parallel with the wire

  7. Turn the voltage on the power pack to a low voltage and switch the power on

  8. Record all readings from the voltmeter and ammeter, and repeat the same experiment for different lengths of the wire

Prework

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Conclusion

Reliability:

The results which I now have are reliable enough to tell me whether different lengths of wire does have an affect on the resistance or not, so in this case, it does.  I have also produced a sufficient amount of results, which are enough to support my conclusion.  

As I have found out that the resistance of a wire is directly proportional to its length, I had done some additional research which also supports this, meaning my results are correct and are reliable.

How to improve Method and Accuracy:

Next time if I had a chance to do this investigation again, I would improve the method by cutting out all the different lengths of wires out individually, so that they would all be exactly the right lengths as they would be straight at the start.  Doing this would improve the accuracy and fairness of the investigation.  The reason why I did not really do this before was because time was against me and that it would be a waste of wire.

Extension to work:

To extend my investigation on the resistance of a wire, I could extend my range of lengths even more so that I would have more results, making sure the pattern of the resistances would be still the same (increasing as the length increases). I could also find out what the cross-section area of the wire is and use the equation I found, which links the resistance with its length, working out whether I would get the same results or not.  If I do, then it would mean that my results are definitely right.

Overall, there isn’t really anything else I could do in order to improve or extend my investigation even more.

Tom Eastman

...read more.

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