What a learner can do afterwards
- Calculates the total resistance of resistors in series and predicts the current
- Explains why two identical resistors in parallel halve the total resistance
- Predicts what happens to supply current when a lamp is added in parallel, and checks it in a circuit
1 · Read
Resistors in series share one path, so the same current flows through each of them. Their resistances simply add: two 10 ohm resistors in series act like one 20 ohm resistor. The supply voltage splits across them in proportion to each resistance.
Resistors in parallel offer extra paths, so the total always falls below the smallest branch. Two identical resistors in parallel halve the total. Each branch feels the full supply voltage, and the supply current rises because charge has more routes at once.
House wiring uses parallel so every socket sees full voltage and one appliance never starves the rest. An old string of lights in series dies together when one bulb fails. Predict each current before you measure, then check with meters.
Each meter has a correct home. An ammeter goes in series because it must carry the current, and a voltmeter goes across the component because it measures the push between two points. Adding a lamp in parallel always lowers total resistance and raises supply current.
Series adds resistance on one path, while parallel adds paths and lowers it.
2 · Watch
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Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.