An electrical circuit was mounted using a power supply, an ammeter, a voltmeter and a resistor (wire). The voltage and current were worked out for different lengths of the wire using the ammeter (for the current) and the voltmeter (for the voltage). Using the voltage and current recordings, the resistances were calculated for each of the lengths. AIM – To investigate the correlation between the length and the resistance of a wire. DIAGRAM – PICTURE – HYPOTHESIS – I predict that the longer the wire, the greater the resistance.
This is because the electrons have to move in a longer distance, making the opposition (resistance) of conductor to the current greater. RESULTS – Tables of results to show the resistance of the wire for different lengths. TRIAL 1 Length (cm) Voltage (V) Current (A) Resistance (? ) Length (cm) Voltage (V) Current (A) Resistance (? ) To work out the resistances of the different sized wires, we used the Ohm’s Law.
The law states that: Voltage (V) = Current (A) x Resistance (? ) SO… Resistance (? ) = Voltage (V) Current (A)So, we first recorded the voltage and current for different sizes of wire, to then work out the resistance of each of them AVERAGE Resistance (? ) Length (cm) Trial 1 Trial 2 Trial 3 Average.
To work out the average resistance for each length, we had to calculate: Resistance of trial 1 + Resistance of trial 2 + Resistance of trial 2 Number of trials (3) e. g. (100cm) Resistance (? ) =GRAPH – *resistance for 80cm wire is a possible anomalous result. CONCLUSION – We can see from both the graph and the results that there is a clear correlation between the length and resistance of a wire: the greater the length of wire lead to a greater resistance. Before analyzing the results, a note must be taken of that the wire started to overheat when it was at about 30cm.
This may have affected the results, as temperature is a factor which can affect resistance, but the truth is that the results of 30cm and 20cm weren’t off the line of best fit in the graph. The only result which was a bit off the line of best fit was the 80cm, in comparison with the other, which can be considered an anomalous result. This could have been caused by an error in recording the results or by the power supply, voltmeter and ammeter not working properly. The results, in general, corresponded to my hypothesis, this because as the length of a wire increased, the resistance also increased.
This is because there is more opposition to the electrons as the wire is longer, as there are more particles opposing to the electrons. EVALUATION – Although the results came as initially expected, the experiment could have been improved in some ways. Firstly, the wire could have been stretched more (in the limit), to give the more precise lengths. As the wire wasn’t fully stretched, the length readings could have been wrong, affecting the current and voltage. To prevent the wire from overheating, we should have decreased the power from the power supply, as temperature increase can also affect the results.
I think that the number of trials was the ideal and repeating it one more time wouldn’t be much useful (although they would be slightly more accurate). Apart from that, I can say that the experiment went well and was a fair test. The results lead to a conclusion very similar to the hypothesis, which shows us that everything went as expected. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.