Required Practical: I–V Characteristics

This lesson covers the AQA Required Practical for investigating the I–V characteristics of circuit components — a filament lamp, a diode and a fixed resistor (AQA 8464, Required Practical Activity 16). Understanding I–V graphs is a very common exam topic.

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Aim

To investigate the relationship between potential difference (V) and current (I) for three components:

1. A fixed resistor (ohmic conductor)
2. A filament lamp (non-ohmic)
3. A diode (non-ohmic, one-directional)

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Equipment

Item	Purpose
Fixed resistor / filament lamp / diode	The component under investigation
Ammeter	To measure the current (connected in series)
Voltmeter	To measure the potential difference (connected in parallel across the component)
Variable resistor or potentiometer	To vary the potential difference across the component
Battery or DC power supply	To provide the potential difference
Switch	To control the circuit and prevent overheating

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Circuit Diagram

flowchart LR
    A["DC Power Supply"] --> B["Variable Resistor"]
    B --> C["Ammeter (A)"]
    C --> D["Component Under Test"]
    D --> A
    E["Voltmeter (V)"] -.->|"in parallel"| D

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Method