Physics · Grades 9–12
Series and parallel: what stays the same · Revision sheet
Use topology before choosing voltage and current rules.
Learn the idea
Series
Resistors in series carry the same current. Their resistances add in the ideal ohmic model.
Parallel
Parallel branches share the same potential difference. Branch currents add at a junction.
Equivalent resistance
For positive resistors in parallel, equivalent resistance is below the smallest branch resistance.
Idealization
Assume ideal wires and source unless internal resistance is specified. This is calculation practice, not a wiring guide.
Explain without looking
- A 12 V ideal source is across a 3 Ω resistor. Find current in that branch.
- Why does equal voltage across two branches not imply equal current?
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.