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To investigate how the resistance of a wire is affected by the length of the wire.

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Introduction

Aim:

In this experiment we are to investigate how the resistance of a wire is affected by the length of the wire.

Background information:

What is resistance?

Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and freer electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and therefore the electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat.

Ohm's Law

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Middle

Power Pack                Crocodile Clips

Variable resistor         Masking tape

Diagram:image03.png

The following circuit was constructed to perform the investigation.


Method:

  1. I set up all the equipment as shown in the diagram
  2. I connected a crocodile clip to the 0cm point and the other one to the 20cm point of the wire.
  3. Then I turned the power pack on and changed the variable resistor to a point that the voltmeter was on 1volt.
  4. I took the measurement of the current flowing through the circuit from the ammeter.
  5. I took the measurements in a table.
  6. Then I did the same but changing the length of the wire.

Fair Test:

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Conclusion

Evaluation:      I think my results are quite accurate, because most of the points are on or close to the line of best fit. Drawing the graph and the line of best fit was easy which shows the accuracy of the results. The first round of testing my results were completely out of order and I had to repeat the test twice. I had no anomalous results, because I repeated everything twice. The experiment could have been done better and more accurate if:

  1. The wire was straighter, so that the measurements were more to the point.
  2. The hot wire had been cooled down before doing another test on it. Heat makes the wire resistance more, because the movement and the collision of the electrons increase.

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This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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