Investigation of how the length of a wire affects resistance.

Variables

• Current flowing through the circuit.
• Length of the wire.
• Thickness of the wire.

Fair Test

• Throughout the experiment the same LVU should be used as different LVU’s give out slightly different voltages.
• Let the ammeter and voltmeter settle before writing down the readings.

Prediction

From my preliminary experiments I can predict that as the wire gets longer the resistance will increase. This is because a long piece of wire will mean that electrons experience more collisions and are therefore stopped more often. This means the current is smaller, so the resistance of the wire must have increased as the length of wire increases.

Analysis

There are no anomalies in my graph, as the points on the scatter diagram fit the line of best fit almost perfectly. I predicted that as the wire gets longer the resistance will increase and my findings support this prediction. The length of wire increased resistance because a longer length of wire means the electrons experienced more collisions and are therefore stopped more often. This meant the current is smaller, so the resistance of the wire must have increased as the length of wire increases.

Evaluation

I decided to take 3 readings of each length of wire so that I could spot any anomalies, however I spotted none. To make my experiment more reliable I could have taken more measurements which would’ve given me a more accurate average. My results would have been more accurate if I had measured the length of wire exactly. During my experiment I could not measure the exact length of wire as it was unsafe to touch the hot wire. Another problem I came across was that as the wire got hotter the length expanded which made it difficult to measure accurately. If I was to repeat the experiment I could improve it by leaving the wire to cool down. Not only would this let me measure the wire more accurately it would ensure that that wire was the same temperature throughout the experiment which could therefore also improve the accuracy of my results.  Another factor which affected the reliability of my results was the thickness of my wire. During our experiment we experienced a problem as the current became too high and the wire snapped. We then tried to continue the experiment using another length of wire which was approximately the same thickness. However, this affected our results dramatically so we had to start the experiment again testing the wire no lower than 20mm long.

Further investigations

The amount of resistance of a material depends on:

• Length of the conductor
• Thickness of material
• Type of material, e.g. wood, plastic
• Temperature (higher temperature/higher resistance)

I have already tested the length of the conductor and the thickness of the material. To further my experiment I could also investigate the type of material and temperature.  I could also test the voltage of the current flowing through the circuit to see how this affects resistance.