Lesson Plan

• Describe how resistance depends on length, cross‑sectional area, and resistivity.
• Explain the proportional relationships R ∝ L and R ∝ 1/A.
• Apply the formula R = ρ L⁄A to calculate resistance for given wires.
• Analyse practical implications for wire selection in heating elements and power transmission.

• Projector or interactive whiteboard
• Slide deck with equations and diagrams
• Sample wires of different lengths and gauges
• Rulers, calipers, and multimeters
• Worksheet with practice problems
• Calculator

Begin with a quick demonstration: connect two wires of different lengths to a lamp and observe the brightness difference. Ask students what they think causes the change, linking to prior knowledge of Ohm’s law. State that by the end of the lesson they will be able to predict resistance changes when length or area varies. Success criteria: correctly use proportionalities and calculate resistance.

1. Do‑now (5’) – Short question on voltage drop and discussion of common misconceptions.
2. Mini‑lecture (10’) – Present R = ρL/A, derive R ∝ L and R ∝ 1/A with visual aids.
3. Guided practice (12’) – Work through Example 1 (changing length) and Example 2 (changing area) as a class; students complete steps on a worksheet.
4. Hands‑on activity (15’) – In groups, measure resistance of provided wires of varying lengths/diameters using multimeters; record data and compare with predictions.
5. Concept check (5’) – Quick quiz (Kahoot/exit ticket) on proportionalities and resistivity.
6. Summary discussion (8’) – Relate findings to real‑world applications (heating elements, power lines) and address misconceptions.

Summarise that resistance rises linearly with length and falls with larger cross‑section, while material resistivity remains constant. Ask each pair to write one takeaway on a sticky note as an exit ticket. Assign homework: calculate resistance for three new wire scenarios and explain which would be best for a power‑transmission line.