Filament Lamp
Filament Lamp Resistance Table
Analysis
Graph 1 – Resistor
The graph for the resistor has a positive correlation. This means that when the current increases so does the voltage. There is a pattern on the Volatge:Current graph for the resistor. For example if we double the voltage then the current also doubles (Voltage 3 to 6, Current 0.35 to 0.7, see graph). This shows that the current through a resistor is proportional to the voltage across the resistor. If I look at the resistance for the ‘resistor’ experiment it nearly stays the same. Apart from the first reading the resistance is all in the range of 8.42-8.74. This shows that the resistor follows Ohm’s law
Graph 2 – Filament Lamp
The graph for the resistor has a positive correlation. This means that as the voltage increases then the current also increases, however this was not at the rate I expected. While the voltage and current increase rapidly first of all, the current soon begins to increase slowly compared to the voltage. For example between 0-1 volts the current increase by 0.31 amps, where as between 9-10 volts the current only increases by 0.04 amps (see graph).
The resistance in the case of the Filament Lamp experiment is very different to the Resistor experiment. In the resistor the resistance stays the same where as the Filament Lamp the resistance increases. This is explained by the fact that the filament lamp increases temperature as the voltage increases. Inside the wire there are positive ions and negative electrons. The negative electrons create the current moving around the circuit. When the voltage is low and the temperature is low, then the positive ions vibrate slowly therefore the electrons can move freely, so the resistance is small.
When the voltage increases and in turn the temperature, the positive ions vibrate (as they have more energy). This means that the electrons find it hard to get through and the resistance increases.
This means that Mr Lawrences Prediction is wrong. As Ohm’s law states ‘that as the voltage doubles, so does the current’ and this does not happen in the case of the filament lamp. I can only say the prediction is partly right as the voltage doubles as the current does in the case of the resistor.