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How Does the Length of the Wire Affect the Resistance?

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Introduction

JOHN PEART

HOW DOES THE LENGTH OF THE WIRE AFFECT THE RESISTANCE?

PLANNING

I am going to conduct an experiment to test the resistance of piece of constantan wire. The main factors that affect the resistance in a conductor are:

  • Length
  • Temperature
  • Cross sectional area
  • Material magnetism

The factor that I am going to change is the length.

Method

I am going to carry out the investigation on a 1metre piece of constantan wire. I am using constantan wire because its resistance is not affected by temperature so I will not have to maintain a steady air temperature. I will set up the equipment listed below.

The equipment I will need for this experiment is as follows:

Power pack

Voltmeter

Ammeter

Bulb

Crocodile clips X2

Wires

1 Metre of Constantan wire

Metre ruler

To begin with I will check that the voltmeter and ammeter both read zero when they are disconnected. This is to ensure that the equipment is working correctly and ensure a fair test.

For each test I am going to use 1 volt.

...read more.

Middle

I will also ensure that no magnetic materials are placed near to the experiment as this may affect the resistance.

Prediction

Metals are good conductors of electricity because they have free electrons to carry the current. I think that the longer the piece of wire is the higher the resistance will be. This is because the resistance in a metal conductor happens because as the electrons move through the material (when a voltage has been applied) they collide with the atoms in the material and as a result loose energy.

Electrical Resistance is the ratio of voltage to current.

To find the resistance you use the equation:

RESISTANCE (R) = VOLTAGE (V) ÷ CURRENT (I)

The temperature of the material will also affect the resistance. A hot metal has a larger resistance than a cooler one. I will not have to worry about the temperature though because I am testing Constantan wire and its resistance is not affected by heat.

...read more.

Conclusion

Cross Sectional Area= πD

        4

        =π x 0.3

        4

        =0.07065 x 10

By using the formula    R=ρ x L

           A

I calculated what my results should be.

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EVALUATION

The experiment was a success. It gave me a go set of results with no anomalous results. The graph and the results table that compares both of the resistivity tests that I did, shows that the results are very similar and the difference is very small. The graph comparing my results with the results that I obtained by using the formula shows that they are very similar which means that my experiment was accurate and successful. From the results I can see that the length of the wire is proportional to the resistance because as the length of the wire increases the resistivity increases. This can be explained because resistance in a metal conductor happens because as the electrons move through the material when a current is passed through it, they collide with the atoms in the material. Therefore if you increase the length the chances of the electrons colliding with the atoms and losing energy is increased.

...read more.

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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