Lesson Plan

• Recall the relationship R = ρL⁄A and define each variable.
• Explain how length, cross‑sectional area, and resistivity influence resistance.
• Apply the formula to calculate resistance for given wire dimensions.
• Analyse the effect of temperature on resistivity and predict the resulting change in resistance.
• Identify and avoid common mistakes when using the formula.

• Projector and screen
• Whiteboard and markers
• Printed worksheet with practice questions
• Assorted copper wires of different lengths and diameters
• Ruler / calipers for measuring diameter
• Scientific calculators
• Handout of typical resistivity values

Begin by asking students why a thin copper wire becomes hotter than a thick one when the same current passes through it. Review that they already know Ohm’s law (V = IR) and the concepts of current and voltage. State that by the end of the lesson they will be able to state the resistance formula, explain each term, and solve a resistance problem.

1. Do‑now (5') – short quiz on Ohm’s law, units, and basic definitions.
2. Mini‑lecture (10') – derive R = ρL⁄A, highlighting the meaning of ρ, L, and A.
3. Guided example (10') – solve the copper‑wire calculation on the board step‑by‑step.
4. Hands‑on activity (15') – students measure length and diameter of provided wires, compute area and resistance using the formula; teacher circulates for support.
5. Concept check (5') – think‑pair‑share: predict how changing length or area would affect R.
6. Temperature discussion (5') – brief explanation of ρ = ρ₀[1 + α(T‑T₀)] and its impact on resistance.
7. Practice questions (10') – students attempt two of the worksheet problems, then peer‑review answers.
8. Quick recap (2') – teacher summarises key points.

Summarise that resistance depends on material, length, area, and temperature, and that the formula R = ρL⁄A quantifies these relationships. Ask each student to write one exit‑ticket response: “State one factor that would halve the resistance of a given wire and explain why.” Assign homework to complete the remaining practice questions and to research the resistivity of an everyday material.