The dependant variable (what I will be measuring) is current.
Method
I will arrange the apparatus as shown in the diagram and cut wires to the following lengths: 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm. I will attach each piece of wire, in turn, to the crocodile-clip leads and set the voltage to 0.4 Volts. This was kept constant throughout the experiment. I will repeat this 3 times for each length of wire and take an average.
I will take 10 readings and my range will be between 10cm and 1metre; I will take each reading 3 times and calculate an average.
I will ensure I have accurate readings by making sure that the room temperature and the temperature of the wire is the same for each test, as heat effects resistance; also that I have accurately measured each piece of wire and that it is the same material because different materials may have different resistances. If the wires were not measured correctly the experiment would be pointless because the results would be faulty.
Prediction
I predict that as the length of the wire increases, the resistance will also increase in proportion to the length.
This is my prediction because the current is the flow of electrons, which is dependant on the amount of voltage applied. Voltage is the push given to the current, which has to go through a circuit containing resistance so if you increase that push you also increase the flow of the current. All materials have a slight resistance to electricity; one of the factors affecting the resistance is length.
- Electricity is a flow of electrons
- Atoms resist having their electrons moved by the electrical energy
- The resistance of the circuit is proportional to the resistance of the electrons to movement
- If the resistors are placed in a line (series) there is more resistance to the flow of electrons
Details of my preliminary experiment
The aim is to ensure that the current can always be read to 2 significant figures, i.e., I > 0.10 A, when L = 1000m.
To ensure that the wire chosen does not get hot, i.e., current I < 1.5 A when L = 10.0 cm
Analysis
From this experiment I have discovered that the over all resistance in a piece of wire is directly proportional the length of the wire. As the length of the wire increases, the resistance increases proportionally.
I have drawn a graph to display my results. My graph is accurate with a best-fit line and anomalous points highlighted.
The trend in my graph indicates as the length of the wire is more, the current becomes less. Mathematically,
