H1 Physics 8867 · objective lesson
Resistance, resistivity and component behaviour
Use V = IR as a definition at an operating point; connect I–V behaviour and temperature-dependent carrier physics to the component.
Repair the common break
Common misconception: Every component has constant resistance.
Correct model: Use V = IR as a definition at an operating point; connect I–V behaviour and temperature-dependent carrier physics to the component.
Worked transfer
At one point on a filament lamp’s I–V curve, R = V/I. As current heats the filament, resistivity rises, so the curve is not a straight line and R is not constant.
Guided practice
Explain why “Every component has constant resistance.” fails. Then construct one example that correctly applies resistance, resistivity and component behaviour.
Independent practice
A wire has length 1.5 m, area 0.20 mm² and resistivity 1.7 × 10⁻⁸ Ω m. Find its resistance and predict the effect of doubling its length.
Return to the recorded repair plan when the explanation and application are secure enough to re-test.