Safety boundary
Use only low-voltage classroom batteries/components under supervision or an approved circuit simulation. Never use mains voltage.
Explicit physics instruction
Current is rate of charge flow. Voltage is energy transferred per unit charge between two points. Resistance describes how strongly a component opposes current under a given model.
For an ohmic component, V=IR. The relation must use compatible units: volts, amperes, and ohms.
A circuit requires a closed conducting path and an energy source; current is not 'used up' as it passes through a component.
Core relation/model: V=IR
Worked example
A 12 V source across a 4 Ω resistor gives I=12/4=3 A.
Guided question
A 9 V source drives 1.5 A through an ohmic resistor. Find R.
Independent work
- Solve three V=IR problems.
- Draw a simple source-resistor circuit.
- State what each variable means physically.
Misconception check
Current is not consumed by a resistor; energy is transferred while charge continues around the closed path.
Formative check
What happens to current if V stays fixed and R doubles?
Reveal response
It halves in the simple ohmic model.
Mentor evidence conference
Ask Archaemenes to audit units, assumptions, model selection, and whether the evidence supports the conclusion.
Teacher guidance
Foundation: Use the Ohm's-law triangle and units.
Core: Solve and interpret V=IR relationships.
Extended: Analyze deviations from ohmic behavior.