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How does changing the length affect the resistance of a wire?

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Introduction

How does changing the length affect the resistance of a wire?

Energy is transferred in a circuit by a flow of charge; this is an electric current. Electric current is measured in amperes (usually shortened to amps or A) using an ammeter. An ammeter is connected in series in the circuit e.g.

The current us always the same in all parts of a series circuit.

The battery (or power supply) provides energy. The higher its voltage the more energy it supplies. The voltage across a component is a measure of the work done, or energy transferred to other forms, when taking the current through a component. Voltage is measured in volts (V) using a voltmeter. Voltmeters are always connected in parallel across a component. A voltmeter in a circuit may look like this:

In series circuits the supply voltage is shared between the components in the circuit.

Resistance is the opposition of a circuit component to the flow of charge.

We can calculate this using the formula:

Resistance (in ohms) = voltage across the resistor (in V)

                         Current through the resistor (in A)

So we can therefore write  R=V/I

Resistance can be measured using this circuit:

The ammeter measures the current in the resistor.

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Middle

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To change the length of the wire, I am going to attach crocodile clips to each of the adjoining wires. I will then move the crocodile clip up and down the given wire depending on the length I wish to measure. The length will range from 10cm-80cm with intervals of 10cm. I decided that the best thickness of wire to use would be 30swg. This is because a thicker wire would cause too much heat, and the resistance of a thinner wire would be too high and difficult to measure. The reason fro this is that a thicker wire has less resistance, because there is more room for the electrons to travel through.

Before carrying out the actual investigation, I feel it is a good idea to carry out a smaller trial run, in order to smooth out any problems I may come across. Ensuring that the wire does not get too hot is an important thing to get right. If the wire gets too hot, energy would be given off as heat, and the resistance would be increased. I did a test that used the same piece of wire at different lengths with a wide range of settings on the power pack.

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Conclusion

The line of best fit clearly show that the results followed the expected pattern very well. The points are very close if not touching the line. This shows how the results were directly proportional through out, as the gradient remained the same.

I feel that the method I used worked very well. I feel it was appropriate and suitable as a way of answering the title question. If I were to do this experiment I would do it just the same, as my results supported my original prediction and gave me a very reliable looking graph. If I were to do an extension piece to this experiment, I would test another factor and see how it also affects the resistance, but keeping the length of the wire constant this time.

I also felt that my data was very reliable also. I did not have any ignored or anomalous readings. Upon repeating readings the results were very close. This tells me that my experiment was very reliable and repeatable. If I were to do it all again my readings would probably come out very similar seeing as all of my points are exactly on the line of best fit. I do not feel that it was just convenient that my results appeared to support my prediction, I feel that this was a conclusive exercise and has a lot more potential in extension work.

Peta Willis 10F        

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