Investigating the resistance of a Nichrome Wire

Apparatus: _                Nichrome Wire – the variable

                        Power supply – to provide the current

                        Variable resistor – to break down the energy

                        Voltmeter – to measure the voltage

                        Ammeter – to measure the current

                        Connecting Wires – to complete the circuit

                        Switch – to complete the circuit

Factors to remain constant:

• Power supply – remain at 2v as it will either overheated or melt the wire.
• Nichrome wire – Although the length will change the wire will stay the same substance as it would not be a fair test to change it.
• Switch – It will always be on, as it completes the circuit and has to stay on for all wire lengths.

Plan: Firstly, I am going to set up a circuit which will consist of an unknown length of wire which will be the only variable, a power supply which will only provide 2 volts for safety, an ammeter to measure the current in amps, a voltmeter to measure the voltage in volts and a variable resistor to break down the voltage for safety. The length of wire will be measured carefully against a metre ruler and 50cm measured. The investigation will be started with 10cm and will be measured with a 30cm ruler. The 10cm of wire will be placed between two crocodile clips which will be connected to the circuit with connecting wires. The variable resistor will be moved each change 2cm using a 10cm ruler. Each measurement will be measured in accurate steps to make the investigation as fair as possible. For each length the voltage and the current will be noted. I will try to keep the temperature constant by keeping it in the same place and making sure it receives the same amount of sunlight. Also I am going to keep the temperature constant by not increasing the voltage throughout the experiment. The circuit will be set up like the diagram above. I will the repeat the experiment to increase the validity of the results and prove the pattern stays the same that as the length of the wire increases so odes the resistance. Throughout the experiment hair will be tied back for safety precautions. Also I have to make sure that the experiment is conducted in an area away from any water as it is a good conductor and s I am using electrical equipment it could be potentially harmful.

Results:  The resistance was worked out by using the formula triangle

By dividing the voltage by the current it obeys the Ohms law.

1st Repeat:

2nd Repeat:

Conclusion: After doing the experiment it was discovered that the prediction made earlier that as the length of wire decreases so will the resistance because electrons travel faster in shorter distances, because there are less atoms stopping the electrons, was correct. However, it was also discovered that as the voltage increased the current decreased, a negative correlation. For example at 10cm the voltage was 0.53 volts and the current 0.22 amps, at 50cm the voltage was 0.85 and the current 0.02. To prove that as the length of wire decreases so does the resistance for example at 50cm the voltage was 0.85 volts and the resistance was 42 and at 10cm the voltage was 0.53 volts and the resistance was 2.41. This proves the prediction was right. On the graph I worked out the average of each length by adding the resistances of each length  and dividing it by three.

Average of 10cm – 7.71 ohms

Average of 20cm – 27.9 ohms

Average of 30cm – 40.6 ohms

Average of 40cm – 75.2 ohms

Average of 50cm – 126.5 ohms

Using the line of best fit you would be able to work out the resistance for different lengths for example at 35cm it would be 60 ohms and at 45cm it would be 94 ohms. This too proves that resistance decreases with voltage, a negative correlation also.

Evaluation: The resistance of a Nichrome wire investigation went very well and so no problems were need to be overcome. The circuit was set up correctly and the lengths of wire measured accurately. There was an anomalous result at 30cm and this may have been anomalous because it was bent on one occasion. This should be checked for to improve the validity of my results. The validity of my results could also be improved by repeating the experiment and seeing if the results would be the same. The result received from this experiment I feel were sufficient to make the conclusion because all measurements were accurate and ohms law was used to workout the resistance.

The investigation could be furthered by trying a wire of a different substance and seeing whether the resistance follows the same pattern. The circuit for that experiment should be setup the same as the one for the Nichrome wire. From doing the experiment it would be discovered that at the same lengths of wire whether the resistance increased or decreased from the resistance of the Nichrome wire revealing that the other substance either had more or less metal atoms than the Nichrome wire or if there was an optimum resistance. Also the factors that affect the resistance could be changed so that we could be able to see the full extent of their affect on resistance.