Current is the same through every component in a series circuit. The supply potential difference is shared between components. Total resistance is the sum of individual resistances, so adding a series resistor reduces current at fixed supply p.d. Example: Correct “the first lamp uses up current”. Charge flow is the same everywhere in series; the lamps transfer energy and share the supply p.d. Rearrange the relationship before substituting if a different quantity is required. Justify your answer.