Lesson Plan

• Describe the relationship between potential difference, resistance, and constant current using Ohm’s law.
• Explain why the p.d. across a conductor rises when its resistance increases while the current remains constant.
• Calculate the p.d. for given resistance and current values and predict the effect of changing resistance.
• Identify material and geometric factors that affect a conductor’s resistance.

• Projector or interactive whiteboard
• Worksheet with practice questions and answer key
• Resistor kit (variable resistor, fixed 24 Ω and 48 Ω resistors)
• Ammeter and voltmeter
• 12 V battery source
• Calculators and rulers

Begin with a quick question: “If we keep the current steady, what happens to the voltage when we use a thicker versus a thinner wire?” Connect this to students’ prior knowledge of Ohm’s law and state that by the end of the lesson they will be able to predict and calculate the voltage change when resistance varies.

1. Do‑now (5') – short quiz on V = I R and the meaning of each symbol.
2. Mini‑lecture (10') – derive V = I R for constant I, illustrate proportionality with simple numbers.
3. Demonstration (10') – set up a series circuit with a variable resistor, keep the ammeter reading constant, and have students record the voltage across the resistor as resistance changes.
4. Guided practice (12') – students work in pairs on worksheet problems calculating resistance, voltage, and discussing material effects.
5. Concept check (8') – think‑pair‑share answering the qualitative question about temperature’s effect on p.d.
6. Summary & exit ticket (5') – each student writes one sentence summarising the p.d.–resistance relationship and solves a numeric exit question.

Recap the direct proportionality between resistance and potential difference for a constant current, highlighting the demonstration results. Collect exit tickets to assess understanding, and assign homework to calculate resistance and voltage for various materials and dimensions.