Ohm’s Law and V-I Evidence
Use V = IR, determine resistance from a V-I best-fit gradient and evaluate experimental evidence.
How to study National 5 Physics
Move from a physical situation to a model, relationship, calculation and evidence-based conclusion, while using current official documents for exact assessment conditions.
Core concepts
Concept 1
Potential difference, current and resistance are related by V = IR.
Exam cue: Check which variable is on each graph axis.
Concept 2
For a V-I graph with voltage on the vertical axis and current on the horizontal axis, the best-fit gradient is resistance.
Exam cue: Choose two widely separated points on the best-fit line.
Concept 3
The resistance of a conductor can change with temperature, so Ohmic behaviour requires appropriate conditions.
Exam cue: State how meters are connected and how heating is controlled in an experiment.
Risk pitfalls and guardrails
Using a data point instead of the best-fit line for gradient.
Guardrail: Check the model, assumptions, prefixes, units, significant figures and whether every conclusion is supported by evidence.
Assuming every component has constant resistance.
Guardrail: Check the model, assumptions, prefixes, units, significant figures and whether every conclusion is supported by evidence.
Connecting an ammeter in parallel or voltmeter in series.
Guardrail: Check the model, assumptions, prefixes, units, significant figures and whether every conclusion is supported by evidence.
Memory anchors
Ohm’s relationship
V = IR.
V-I gradient
Resistance when V is vertical and I horizontal.
Ammeter
Connected in series.
Voltmeter
Connected in parallel across the component.
Temperature effect
Resistance of a conductor changes as temperature changes.
Best-fit gradient
Use two separated points on the line, not necessarily raw points.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A 12 V p.d. drives 3.0 A. Resistance?
What potential difference is across a 15 Ω resistor when its current is 0.40 A?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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