My aim for this investigation is to experiment and find out whether the length of a copper wire in a circuit affects the amount of resistance.

Prediction:

I predict that the longer the wire, then the more resistance there is. This results in less current flowing around the circuit. I predict this because metals conduct electricity in a special way. Metals have atoms which have a weak force of attraction between them and the electrons. Resistance is caused when these electrons flowing towards the positive terminal have to ‘jumps’ atoms. So if we double the length of a wire, the number of atoms in the wire doubles, so the number of jumps doubles, so twice the amount of energy is required: There are twice as many jumps if the wire is twice as long. Electrons moving through the short wire only feel resistance for a short time compared to the longer one. This means its resistance is less.

To work out the resistance of the wire, I will divide the Voltage (V) by the Current (A).

The ‘I’ represents Resistance. And the

‘A’ represents Current:

Preliminary work:

In this preliminary, I will determine how much wire to use in the actual investigation. This helps because it will tell me exactly how much wire to use in the real investigation to efficiently support my prediction.

Here are the results of my preliminary:

 

My preliminary work results show that the resistance of the wire DOES go up as the length of the wire goes up. However, as this is a preliminary, there could be a lot of mistakes. So to reduce these mistakes, I have chosen to repeat the experiment three times rather than once as was in the preliminary.

Also there were too many results, so I am going to experiment with only lengths of wire in the multiple of ten, up to eighty. This will reduce the number of results I get, but will still clearly give an indication whether my prediction is correct or not.

Plan:

My plan for the investigation is to set up the circuit as follows:

1. I will connect a battery to an ammeter. I WILL BE USING 1 BATTERY FOR THE EXPERIMENTS.
2. I will then stick copper wire onto a metre ruler
3. I will clip one end of the wire with a crocodile clip
4. I will clip the other end of the crocodile clip at another point of the crocodile clip. This point and the end of the copper wire will be equivalent to the length of the wire I am currently investigating.
5. I will connect the voltmeter in parallel.

I will conduct the experiment three times for every measurement of the wire to avoid any mistakes. I will also make sure the only variable is the length of the wire. As an extra precaution and to achieve the best possible results, I will change the ammeter and voltmeter after every run of the experiment. To make this test fair I should take more than one result so that I can work out an average, this will help prevent any wayward results.

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Results Table:

Here are my results for the experiments:

To calculate the resistance, I have divided the voltage (V) by the current (A). This gave me the resistance. To calculate the average resistance, which will be used to see if my prediction is right, I added all the resistance results and divided by 3 to get the average resistance. I will now interpret the graph here:

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Conclusion:

From the data above, I can conclude that my prediction was correct - that resistance is increased if the length of the wire ascends. This results in a less current round the circuit.

One way the results could have been inaccurate is that I could not keep the temperature of the wire under control. As explained as one of the factors, temperature does make a difference to the resistance. One way I could have overcome this problem is to use a fresh batch of wire every time I conducted the experiment. This way all the wire temperature will be the same.

The higher the resistance, the less current passes through it.

Evaluation:

I enjoyed working and investigating my prediction. My results could have been improved if I have used a fresh batch of wire for each experiment. This would make sure the temperature was the same for each experiment.

Another way I could have improved my results was to use a different set of equipment for each investigation, as some of the equipment was out-of-date, so they are prone to give inaccurate readings, which will affect my results.