Required Practical 16: I-V Characteristics

About this practical...

This is another great way to learn about circuits and how potential difference (voltage) affects the current through the wires. You need to measure how these two variables behave through resistors, filament bulbs and diodes. To ensure that any effects are due to the changes you make, temperature must remain constant. (Remember that filament bulbs produce light because they get hot, in a most homes now, filament lamps are things of the past).


1. Collect all of the equipment needed to make up the circuit shown.

2. Construct the circuit, ensure that the ammeter is in series and that the voltmeter is in parallel.

3. Turn on the power supply (DC 4V) and adjust the variable resistor until the voltmeter reads 0.5V. Record the current.

4. Adjust the variable resistor until the voltmeter reads 1.0V and record the new current.

5. Continue until you reach 4.0V. You can then repeat all of these results so that you can spot anomalies, remove them and calculate a mean.

Ensure that you turn off the power supply between readings as the current will generate heat in the conductors which will change the resistance.

Plot a graph of Potential Difference (x-axis) against Resistance (y-axis). This will show if the resistor is an ohmic conductor.

Safety & Managing Risks

Usual lab rules must be followed: Bags and stools tucked away and notify the teacher of any breakages immediately. Take care with sources of electricity. The wires will become hot if you create a short circuit so follow the circuit diagrams carefully. Bulbs may become hot. For more detailed information, please consult CLEAPSS.

Technician notes:

Powerpacks (limited to 6V)




Variable resistors

This page was updated on: 8th January 2022