Physics coursework - Sample Essay
The purpose of this investigation is to carry out two experiments, collecting a series of data. This will then be analysed and a conclusion will then be drawn, using my knowledge of physics. The purpose of the experiments conducted was to investigate the relationship between resistance and the dimensional properties of Nichrome wire. In both experiments the circuit was set out as illustrated below. The wire used had a single strand cross-sectional area of 33×10 cm. Experiment 1: Length & Resistance The first experiment explored the relationship between the length of wire and resistance.
The different lengths of wire used ranged form 10cm to 100cm. A current was run through the circuit and the resistance across the wire was measured using an analogue meter. This data was then tabulated as shown below. Length (M) Volts (V) Amps (mA) Ohms R=V/I Resistance/Length It is very difficult to analyse, and extract relationships from the initial table, so I decided to plot these results on a graph. When conducted, the trials were not performed in uniform increments. I decided to create another set of results, showing only results that were of increments of 10cm. I have also graphed this modified set of results, as it will allow me to extract more clear and accurate relationships.
The initial table also illustrates that the input voltage varied in some of the trials. This was a deliberate modification, with the aim to prevent a dramatic increase in the temperature of the wire. This change in input voltage would not have had an effect on the resistance. As the potential difference changes, the current changes proportionally. Therefore, when calculated the resistance amounts to the same value. The resistance is calculated using the equation: R = V i?? I Where: R is resistance (? ) V is potential difference (V) I is current (A) Analysis of Results.
Due to the nature of the equipment, the results of the experiment are not completely accurate. However, correlations and relationships are still clearly illustrated as shown in the initial graph below. The above graph shows a very vague proportionality between length and resistance of wire. Error bars have been used in this graph. However, the resolution of the meter is approximately 0. 2%, so they may not be clearly visible. This supports the theory that when wire is shorter, the same number of electrons are trying to pass through less wire. This results in them being bunched together trying to push through.
One major factor to take account of is the fact that analogue meters were used in the experiment. These have an error margin of approximately 0. 1%. These meters have a very poor scale and are not calibrated in the same way that digital meters are. This is exemplified in the initial graph of results (in the appendix), where the resistance plots regress from the line considerably. Other systematic errors include the effect of heat on resistance. Nichrome wire has a positive temperature co-efficient, meaning that resistance rises with temperature.