Lesson Plan

• Describe the definition of electromotive force and potential difference in terms of energy per unit charge.
• Explain how e.m.f. and p.d. differ in location, sign convention, and measurement conditions.
• Apply the energy perspective to calculate work done by a source and by a circuit component.
• Analyse a simple circuit to determine internal resistance using e.m.f. and terminal voltage measurements.
• Compare and contrast e.m.f. and p.d. using a comparison table.

• Battery with known e.m.f. and internal resistance
• Resistors of various values
• Digital voltmeter (two units)
• Ammeter or multimeter
• Connecting wires and breadboard
• Worksheet with comparison table and calculation tasks
• Projector for displaying diagrams

Begin with a quick question: “If a battery supplies 12 J of energy per coulomb, where does that energy go?” Connect this to prior knowledge of voltage as energy per charge. State that by the end of the lesson students will be able to clearly differentiate e.m.f. from potential difference and justify the difference using energy considerations.

1. Do‑Now (5'): Students answer a short prompt on work per charge; teacher reviews responses.
2. Mini‑lecture (10'): Define e.m.f. and p.d., present the energy equations, and display the comparison table.
3. Guided demonstration (10'): Measure open‑circuit voltage (e.m.f.) then terminal voltage with a resistor; calculate internal resistance together.
4. Collaborative activity (15'): Groups complete a worksheet calculating energies, filling the comparison table, and interpreting results.
5. Check for understanding (5'): Exit ticket – one concise sentence distinguishing e.m.f. from p.d.; collect for assessment.

Summarise that e.m.f. represents the source’s ability to do work inside the source (open‑circuit), whereas potential difference measures the work done across external components (closed‑circuit). Collect the exit tickets and assign a homework problem requiring students to determine the internal resistance of an unknown battery using measured e.m.f. and terminal voltage.