The voltage across and the current through a component (eg a filament lamp) can be measured and the results plotted on a graph to show the I-V characteristic of the component. In this practical activity, it is important to measure and observe the voltage and current accurately.
An example results table may be:
|Voltage (in V)||Current (in A)|
Plot a graph of current (y-axis) vs voltage (x-axis), which should look like this.
In a filament bulb, the current does not increase as fast as the voltage. Doubling the amount of energy does not cause a current twice as fast.
The voltage is not directly proportional to the current, so the graph is not a straight line. As the current through the lamp increases, the filament gets hotter and has a higher resistance. It is not an ohmic conductor.
|Hot lamps can burn||Burns to the skin from hot lamps||Do not touch the lamp whilst the circuit is connected; allow time for the lamp to cool|