AQA GCSE FOUNDATION PHYSICS - I-V Characteristics of Circuit Components

Investigating I-V Characteristics of Circuit Components

This tutorial will guide you through the process of investigating the relationship between current and voltage for different circuit components. This is known as the I-V characteristic of the component.

What You Need

• A power supply
• A digital multimeter (DMM)
• A range of circuit components (e.g., resistors, filament lamps, diodes)
• Connecting wires
• A circuit board (optional)

Setting Up the Experiment

1. Connect the circuit:
   • Connect the positive terminal of the power supply to one end of the component.
   • Connect the other end of the component to one terminal of the DMM.
   • Connect the other terminal of the DMM to the negative terminal of the power supply.
2. Set the DMM:
   • Set the DMM to measure current (A) for one terminal.
   • Set the DMM to measure voltage (V) for the other terminal.

Taking Measurements and Plotting the Graph

1. Increase the voltage: Start with a low voltage and gradually increase it in small steps.
2. Record the readings: For each voltage setting, record the corresponding current reading.
3. Repeat: Repeat steps 1 and 2 for a range of voltage values.
4. Plot the graph: Plot the current (I) on the y-axis and the voltage (V) on the x-axis.

Analyzing the I-V Characteristics

1. Resistor

• Linear relationship: The graph for a resistor will be a straight line passing through the origin.
• Ohm's Law: This indicates that the current is directly proportional to the voltage, as stated by Ohm's Law (V = IR).

2. Filament Lamp

• Non-linear relationship: The graph for a filament lamp will be a curve, starting off relatively linear at low voltages, then curving upwards as the voltage increases.
• Resistance increase: This is because the resistance of the filament increases as it gets hotter.

3. Diode

• One-way conduction: The graph for a diode will show a large current flow in one direction (forward bias) and a very small current flow in the opposite direction (reverse bias).
• Forward voltage: There will be a small voltage threshold (forward voltage) that needs to be overcome before the current starts to flow significantly in the forward direction.

Conclusion

By plotting the I-V characteristics, you can gain insights into the behavior of different circuit components and understand how they respond to changes in voltage. This knowledge is crucial for designing and analyzing electrical circuits.