To carry out my investigation I will need a power supply, ammeter, voltmeter, crocodile clips, connecting wires and nictrome wire. I will set up my apparatus up as shown in the diagram.
To start my investigation I am going to set up my apparatus; as in the diagram. I will start by measuring 10cm of wire using a ruler; I can then connect the crocodile clips to both ends of the 10cm wire and turn the power supply on. When I have done this the reading on the ammeter will give the current, and the reading on the voltmeter will give me the voltage. I need these two readings to work out the resistance. When I have got both of my readings I will turn off the power supply and increase my wire to 20cm using a ruler, and then get the information to work out the resistance, as before. Each time I start a new investigation I will increase the length of wire by 10cm. When I have reached 100cm/1m I am going to stop, but to make my results reliable I am going to repeat the whole investigation again.
When calculating the resistance I will need the current (reading on ammeter), and the voltage (reading on voltmeter) I can then work out the resistance by dividing the voltage by the current:
Resistance = voltage
Current
To do my investigation accurately I will need to carry out fair experiments, to make these fair I will need to keep the same type of wire and the same thickness for each experiment. I also need to make sure the voltage on the power supply is the same. I also need to measure the length of the wire with a ruler and make sure the current is flowing through only one wire. To make my results accurate I am going to round my numbers to two decimal places, also the results must be reliable so I will repeat the investigation twice. When doing my experiments I will make sure that I do them safely, I can insure the safety by turning the power supply off each time I have finished an experiment, I will also make sure the amount of voltage through the wire is not too high so the wire becomes overheated.
Obtaining results
Investigation one
Investigation 2
Average of two investigations
Analysis of results
These are my results for the two investigations I have done. I have also included three graphs which show both experiments and one showing the average. In my graphs I have also included a line of best fit.
When looking at my result tables and graphs I have noticed a pattern. When we double the length the resistance doubles. This happens in all of my graphs and can be clearly shown in investigation two, because when I doubled the length of 20cm to get 40cm, I also doubled the resistance 0.25 to get 0.50. From my graph I can also state a conclusion which shows that as you increase the length of the wire the resistance increases too, this shown by my line of best fit as the resistance is proportional to the length.
I can see that my conclusion agrees with my prediction. I said that when we increased the length by 10cm the resistance would also increase. This happens because as the length doubles the number of atoms doubles which causes collisions with electrons and slows the flow of electrons through the wire causing an increase in resistance.
Evaluation
I think I carried out my investigation accurately therefore I produced accurate results, and I think that repeating the investigation twice was enough. I think the best part of my investigation was obtaining my results, because when looking at my table of results and my graphs there are no anonymous results. I think this happened because we were accurate when doing each experiment and kept all the tests fair. I also think our practical work went well because we followed what we originally intended on doing and made no changes during the investigation. To improve my investigation I would take more accurate readings from the ammeter and voltmeter and round the number to one decimal place. To further my investigation I would use thicker and different types of wire. Overall I think the experiment went well as my results and prediction supported my conclusion
