Changing the length of a wire and how it affects the resistanc - GCSE Coursework

Variables and Fair Tests – I will take 3 results per length, i.e. 3 results for copper wire 0.2, 3 results for copper wire 0.4 etc, in all the different types of wire.

It is good to repeat each result 3 times because this means that if I have made a mistake I will notice it more easily.

During the experiment I will be changing the length of the wire and the type of wire, these are called variables.

Equipment List –

• 10 wires
• 2 crocodile clips
• copper wire
• iron wire
• constantan wire
• voltmeter
• ammeter
• power pack
• pen and paper for recording results

Method –

1. First I need to collect all the equipment and prepare my work surface. The first wire I am going to test is copper. I need to set the circuit out as below:

2. When the power pack is plugged in, I need to turn it on and set the voltage. I then need to attach the wire so the crocodile clips are attached at the length of 0.2m

3. Once the wire is attached at 0.2m I need to run the power through. I then need to write down the voltage and the amps onto my results table.

4. I can then repeat steps 2 onwards for the next measurement (0.4m) until I have all the results for all the lengths of wire for copper.  

5. Once I’ve done this I can repeat for the constantan and iron wires.

The following page shows my results from the preliminary test:

Preliminary trial run results for copper:

Preliminary trial run results for iron:

Preliminary trial run results for constantan:

Here are the results from my preliminary experiment together on one graph so I can compare which is best.

The Resistance of 3 different wires:

When I did my preliminary I decided to choose constantan wire. I chose this because it gave me the best range of results and the easiest results to work with.

My Main Experiment - Now I have tested the experiment in my preliminary experiment I can use things I have learnt to improve my next experiment.

Method –

1. First I need to collect all the equipment and prepare my work surface. I need to set the circuit out as below:

2. When the power pack is plugged in, I need to turn it on and set the voltage. I then need to attach the wire so the crocodile clips are attached at the length of 0.2m

3. Once the wire is attached at 0.2m I need to run the power through. I then need to write down the voltage and the amps onto my results table.

4. Once I’ve written down my first results I need to repeat it so I have 3 different results. This means I can create an average current and average voltage to achieve the best results.

5. I can then repeat steps 2 onwards for the next measurement (0.4m) until I have all the results for all the lengths of wire.

My results from the main experiment are as follows:

Here is a graph to show my results. By using my graph I can predict what results for other times might be by extending the line. I have chosen to put a line of best fit.

A Graph to show the results from my first table of results:

A Graph to show the results from my second table of results:

A Graph to show the results from my third table of results:

Graph Analysis - The graph above shows my results from the experiment. You can see that the points create a fairly straight line. I have drawn a line of best fit on the graph to help me predict what the other results will be. I can extend the line out to see how long it will take other temperatures to react.

There were no anomalies in my results as they all followed the line of best fit.

My results followed a pattern. The pattern was that the lowest lengths had the lowest resistance and the higher lengths had a much higher resistance. I predicted that when the length of the wire increased, so would the resistance. I thought that because the longer the wire, the more energy the electrons use up when they go around the circuit.

Evaluation - The method I used I thought was effective because the circuit was easy to change the length of the wire (simply by re-clipping the crocodile clip to make it shorter) My results are quite precise and accurate and there were no anomalies so I think I that the experiment when according to plan. I followed through my method accurately and produced accurate results.