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The aim of my investigation is to find out how the length of a wire affects its resistance, by carrying out an experiment.

Extracts from this document...

Introduction

  PHYSICS

SCIENCE

COURSEWORK:

How the length of a wire affects its resistance.

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By Maria Dela Cruz

By Maria De La Cruz

Aim:  

The aim of my investigation is to find out how the length of a wire affects its resistance, by carrying out an experiment.

Scientific Knowledge:

Current passes easily through a piece of copper connecting wires.  However, current does not pass as easily through a thin nichrome wire of an electric fire element.  Therefore, the nichrome wire has more resistance.  Energy that has been used up, force electrons through it, and when this happens, heat comes off as a result.

All conductors have some resistance, but:

  • Short wires have less resistance than long wires
  • Thick wires have less resistance than thin wire.
  • Copper wire has less resistance than nichrome wire that are the same size.

This is all because, as the electrons in an electric current move around a circuit, they bump into atoms and other electrons in the wires through which they pass.  Atoms of different elements hold up (impede) to electrons to different extents.  For example, electrons pass easily through copper wire, but much less easily through nichrome wires.  We say that copper has a lower resistance than nichrome.  This is why copper is used for the connecting wires and cables in electric circuits.

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Middle

When the equipment is all set up, get the piece of nichrome wire.  Using a meter ruler, measure the wires length starting from 10cm.Place crocodile clips at the end of the connecting wires, so that you can connect the connecting wires to the nichrome wire, at the 10cm measurement.When ready, make sure that the power pack is set at direct current (d.c.), and at the power of only 2.Turn on the switch and the power pack.When the voltmeter is not constantly flickering, record the voltage.  Remember, this voltage has to be kept the same all through out the experiment, using the variable resistor.  Record the current, which is shown in the ammeter.Turn off the switch and the power pack.Repeat steps 1-8, using the measurements 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and finally 100cm.  Repeat the whole experiments again from the beginning, for reliability and accuracy of your results.  

Fair Test:

To keep my experiment as fair as I can, I will try to do the following things:

  1. I will keep the same wire I will use all through out the experiment.  This is because using a different wire can affect the results.
  2. I will keep the same thickness of the wire.
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Conclusion

Kinks developed in the wire when they are coiled.Problems getting the voltage the same using the variable resistor.Difficulties putting all the wire in the beaker of water, causing the temperature to go up in different parts of the wire.

Accuracy 2:

This is how I could make my results accurate:

  1. Pull nichrome wire to straighten it, before measuring the nichrome wire.  This way it is stretched and can be measured more accurately.
  2. Selotape the nichrome wire to a ruler when measuring.  This way the wire will not move as you measure it and can be measured more accurately.
  3. Using tips of the nails or fingers move it along the wire to straighten out the kinks that might prevent it from being accurately measured and giving me accurate results.
  4. Use sensitive voltmeters and ammeters so there is no continues flickering, and that the results could be more accurate.

This is another accuracy I have added because the experimental errors I have got were due to the fact that the voltmeter and ammeters continuous flickering.

Conclusion:

In conclusion, I think that my results were good but not perfect and accurate enough.  Due to the problems, some results became anomalous and errors appeared during the experiment.  Therefore, I go not think my results are reliable but still prove that resistance is affected by the length of the wire.  It is affected because as length gets longer the resistance increases.  

Maria De La Cruz

...read more.

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