Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain what resistance measures and state its unit, 1 Ω = 1 V/A. (Guide: “What resistance measures”)
- I can explain the difference between resistance (an object) and resistivity (a material). (Guide: “Resistivity is a property of the material”; Practice Q2)
- I can explain why the resistivity of a metal usually rises with temperature. (Guide: “Resistivity is a property of the material”; Practice Q5)
- I can state Ohm’s law and say what makes an element ohmic or non-ohmic. (Guide: “Ohm’s law”; Practice Q5)
- I can explain that a resistor converts electrical energy to thermal energy, which may warm it and its surroundings. (Guide: “Resistivity is a property of the material”)
Calculation and skills
- I can derive R = ρℓ/A from E = ρJ and ΔV = Eℓ. (Guide: “From E = ρJ to R = ρℓ/A”)
- I can calculate the resistance of a round wire, converting the diameter to a radius in metres. (Guide: Worked example 1; Practice Q4)
- I can find the resistance of a wire whose resistivity varies, using R = (1/A)∫ρ(x) dx. (Guide: Worked example 3; Practice Q7)
- I can plot I against ΔV with sensible scales and units, draw a best-fit line and find R = 1/slope. (Guide: Worked example 2; Practice Q1)
- I can plan an experiment to measure resistivity and find ρ from the slope of R against ℓ. (Practice Q6)
Reasoning
- I can predict the factor by which R changes when a wire’s length, diameter or material changes, or when it is stretched. (Practice Q2, Q3)
- I can decide from data whether an element is ohmic, and find R at a point on a curved graph from ΔV/I. (Guide: Figure 1; Practice Q5)
- I can explain how a potential difference is shared along a wire whose resistivity varies, using the same current in every slice. (Guide: Worked example 3; Practice Q7)
All ticked? Move on to Topic 11.4, Electric Power, or return to the course roadmap.