Whereas the shorter the wire, the less ions. This means the electrons have fewer ions to collide with and less energy is lost. Therefore, the shorter the wire, the higher the current.
The electrons are usually drawn to show that they move from the positive side to the negative.
However, the electrons actually flow from the negative side in the direction of the positive.
Aim
My aim is to investigate how the length of a wire affects the current that flows through it.
Prediction
I predict that the shorter wire will allow the most current through. This is because the shorter the wire, the less ions there are for the electrons to collide with and lose energy. If the electrons lose energy, the current slows down and reduces.
Therefore, the longer wire will allow the least current through. This is because the longer the wire, the more ions there are for the electrons to collide with and lose energy. If the electrons lose energy, the current slows down and is reduced.
Diagram
Method
Apparatus List
Power Pack
Ammeter
Voltmeter
Crocodile clips
110cm of constantan wire
100cm (1m) ruler
- Plug the power pack into an electricity supply.
- Connect the crocodile clips to the power pack.
- Connect the voltmeter in parallel within the circuit.
- Connect the ammeter in series within the circuit.
- Set the voltage to 3 volts and to direct current.
- Have the ruler ready.
- Measure 40cm of the wire. Wrap the extra wire around the crocodile clips.
- Turn the power pack on and read the voltmeter and ammeter readings.
- Record the results
- Repeat this for different measurements of wire with 10cm intervals.
- Record the results
- Repeat all the readings with the same measurements as before.
- Record the results in a clear table
- Calculate the resistance and average current from the results.
Fair Test
To keep my experiment fair, I will attempt the following things.
I will have just one variable in the experiment, which is the length of the wire. The wire that I use will be the same type (constantan) and have the same diameter for each experiment. I will keep the voltage the same each time. I will have more than 100cm of wire for the crocodile clips and I will try to keep the wire as taunt as possible. I will make sure that the readings stop fluctuating before I take the following readings. I will also keep all the equipment the same.
Results Table
Formula
Average Current = 1st reading +2nd reading
2 (amount of readings
Resistance = voltage (V)
current (A)
Conclusion
My results show that the longer the wire, the less current flows through it. My results also show that the longer the wire, the higher the resistance. This is because the longer the wire, the more positive ions in the wire. Therefore there will be more collisions between the electrons, causing a decrease in current. The shorter the wire, the less positive ions for the electrons to collide with and lose energy.
These results support my original prediction, which was,
The shorter wire will allow the most current through and the longer wire will allow the least current through.
The resistance steadily rises as the length of the wire increases. From 40cm to 100cm, the amount of resistance has almost doubled. As the length of the wire increases, the current flowing through the wire steadily decreases. The amount of current in the 100cm of wire is over double compared to that of the 40cm wire. Although the results are not increasing or decreasing at a steady rate, they do prove my original prediction.
On my current graph, the first three results prove to be inversely proportional to an increase in the length of wire. On the resistance graph the first three results prove to be directly proportional.
Evaluation
My experiment was fairly successful as I developed a correct conclusion from my results, although there were a few anomalous results. On the current graph these anomalous results were for the 60cm result and also the 100cm result. These results do not fit the line of best fit perfectly. They do not follow the curve of which the other results fit into. On the resistance graph there is an anomalous result also for the 60cm result. Therefore my graphs weren’t directly or inversely proportional. This could be due to a few things.
Firstly there was not a perfect constant voltage, causing a slight increase in current. Kinks in the wire could prove to give inaccurate results, as the length would not be exact. Also, the room temperature had not been monitored, which could affect the final results.
To make my results more accurate I could take more ammeter and voltmeter readings, which would give me a bigger range of results. I could also conceive a way of which to connect the wires to the crocodile clips without wrapping it, as this causes kinks in the wire.
