Safety boundary
Use only low-voltage classroom batteries/components under supervision or an approved circuit simulation. Never use mains voltage.
Explicit physics instruction
Electrical power is the rate of energy transfer. For circuit elements, P=VI and can combine with Ohm's law into P=I²R or P=V²/R when the ohmic model applies.
Energy transferred over time is E=Pt.
Power ratings describe transfer rate, not total energy by themselves.
Core relation/model: P=VI; E=Pt
Worked example
A 6 V device drawing 2 A uses 12 W. In 30 s it transfers 360 J.
Guided question
A 9 V component draws 0.5 A for 20 s. Find power and energy.
Independent work
- Solve three power problems.
- Convert one power-time result to energy.
- Compare two devices at equal voltage.
Misconception check
A watt is a rate unit, not an energy unit.
Formative check
What extra quantity is needed to convert power into energy?
Reveal response
Time.
Mentor evidence conference
Ask Archaemenes to audit units, assumptions, model selection, and whether the evidence supports the conclusion.
Teacher guidance
Foundation: Calculate P=VI.
Core: Combine Ohm's law with power.
Extended: Compare efficiency and thermal loss in circuits.