Required practical · AQA, EDEXCEL, OCR
Required practical: Determine the resistance of a component (I–V characteristics)
Aim
To measure current through and potential difference across a resistor (or lamp), calculate resistance, and plot I–V to identify ohmic vs non-ohmic behaviour.
Method (step-by-step)
- Wire in series: cell/battery, ammeter, component; voltmeter in parallel across the component.
- Vary supply or use a variable resistor to change p.d.; record I and V pairs.
- Repeat for a lamp and compare shape — filament heats, resistance changes.
- Plot I vs V (or V vs I per spec) and interpret gradient.
Equipment
- Ammeter
- voltmeter
- wires
- power supply
- resistor / lamp
Variables
- Independent: Potential difference across the component.
- Dependent: Current through the component.
- Control: Same component; same temperature where possible; same wiring
Results & analysis
For ohmic conductor, straight line through origin (constant R). Lamp curves due to temperature.
Graphs & interpretation
Gradient meaning depends on axes — state R = V/I clearly for your graph orientation.
Common mistakes (high yield)
- Swapping ammeter and voltmeter positions.
- Taking only one reading.
- Using mean of V/I without checking line is straight.
Exam-style question prompts
- Why does a filament bulb not obey Ohm’s law?
- How reduce systematic error?
Exam tips
- Units: A, V, Ω
- Hot filament → higher resistance
Related topic revision
FAQs
Exam boards differ in wording; always follow your specification and your teacher’s practical notes. Back to GCSE Physics required practicals hub.