Safety boundary
Use only low-voltage classroom batteries/components under supervision or an approved circuit simulation. Never use mains voltage.
Explicit physics instruction
In a series path, the same current passes through each component and voltage drops add to the source voltage.
In parallel branches, the same potential difference appears across each branch while branch currents add to total current.
Equivalent resistance depends on arrangement; adding a series resistor increases total resistance, while adding a parallel branch can reduce equivalent resistance.
Core relation/model: series: R_eq=ΣR; parallel: 1/R_eq=Σ1/R
Worked example
Two 3 Ω resistors in series give 6 Ω. The same pair in parallel gives 1.5 Ω.
Guided question
Compare equivalent resistance for 4 Ω and 12 Ω in series versus parallel.
Independent work
- Compute equivalent resistance for three networks.
- Predict current/voltage patterns.
- Explain one result with a junction/loop argument.
Misconception check
Parallel branches do not 'split voltage' the way series components do; branch voltage is shared across the same two nodes.
Formative check
Which arrangement gives lower equivalent resistance for the same two positive resistors?
Reveal response
Parallel.
Mentor evidence conference
Ask Archaemenes to audit units, assumptions, model selection, and whether the evidence supports the conclusion.
Teacher guidance
Foundation: Trace one series and one parallel circuit.
Core: Calculate equivalent resistance and current patterns.
Extended: Analyze mixed networks qualitatively.