The experiment I have chosen to carry out will record whether the length of a wire will affect the resistance in a complete circuit. I will set up an experiment, setting up a complete circuit

I predict that as the length of the wire increases, the current flowing through the wire will decrease, the voltage will increase and the resistance will increase. I am sure the resistance will increase because it is a measure of how difficult it is to push electrons through a wire. The larger the resistance, the more force you have to apply and the more energy you use to produce a current. The process is similar to the resistance you feel if you try to blow water through a straw or a hose. You have to blow harder to push water through a long hose, and you also have to work harder if the hose if very small in diameter.

The first sets of results that were taken, (the preliminary expt.) were fairly accurate, but there are many things that had to be improved upon:

• We did not measure up to a full metre
• The voltage we set the power cell on to start was too high. The wire glowed red hot. We had to change it to a suitable voltage.
• We did not measure the wire accurately enough. In the next experiment it could be improved by sellotaping the wire straight up against a metre stick so we could get the most accurate length possible.

Preliminary experiment:

Two more experiments were carried out after the preliminary experiment. They followed instructions exactly.

Results:

Experiment 1:

This graph clearly shows that as one increases, so does the other. The results we have collected show us that the length of a wire will affect the resistance in a complete circuit.

We had a very clear and accurate set of results with only one anomaly. The only one was as follows:           cm                       current               voltage               resistance

Although the voltage increased and then decreased, the resistance still increased, as was predicted. This type of anomaly was not anticipated but it did not make much difference at all to the results.

The resistance increased because, as was mentioned in the prediction, resistance is a measure of how difficult it is to push electrons through a wire, so the larger the resistance, the more force you have to apply and the more energy you use to produce a current. This is why the voltage went up whilst the current went down.

The resistance of a wire is: R = r × L÷A.

L is the length of the wire, A is the cross-sectional area of the wire, (Of course, to get the most accurate results possible when applying this equation, we should make sure that the cross-sectional area of the full length of the wire is known.) and r is the “resistivity” of the material. Long, thin wires have the most resistance, just like long, thin pipes.