Series and Parallel Circuits
AdvancedSeries has one current path — one break stops all and bulbs dim; parallel has branches — one break leaves the rest on. Home appliances are all in parallel.
- Series: one path — one break stops all, and bulbs are dimmer.
- Parallel: branches — one break leaves the rest on, each bulb at normal brightness.
- In series the battery voltage is shared among the bulbs.
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§Text Passage
1Two bulbs and a battery on the bench: join the bulbs end to end in one line, or give each its own branch. The first is series, the second parallel — and the two behave completely differently.
2A series circuit has a single path: current passes through every component in turn, each bulb receives only part of the voltage and glows dimly; one break extinguishes everything. A parallel circuit splits into branches at a junction: every branch gets the full battery voltage, bulbs shine normally, and a broken branch leaves the others untouched.
3Our homes are a world of parallel wiring: lights, fans, fridges and TVs switch on and off independently. Imagine series wiring instead — switching off one lamp would stop every appliance, and one burnt bulb would black out the whole flat.
4Parallel brings convenience, but filling one socket with appliances raises a new question: what if the current gets too large? The next lesson covers electrical safety.
1Summary 重點摘要
Series has one current path — one break stops all and bulbs dim; parallel has branches — one break leaves the rest on. Home appliances are all in parallel.
2Vocabulary cards Vocabulary
Components joined end to end so that current has only one path.
A connection where the current splits and flows through two or more branches.
One of the separate paths available to the current in a parallel circuit.
The point in a circuit where the current splits or rejoins.
How strongly a bulb shines: bulbs dim in series but each keeps near-normal brightness in parallel.
A break that stops the current: in series everything stops, in parallel only that branch stops.
The parallel connection of home appliances so each can be switched independently.
In parallel the total current divides at a junction, each branch taking a share.
3Step by step Steps
- Series: one single pathSeries means joining components end to end so the current has only one route: connect two bulbs one after another to a battery and the current passes through both in turn. The same current flows through every bulb — the defining feature of series. But the two bulbs share the battery's voltage, each receiving only half, so both shine dimmer than a single bulb. Old-style Christmas light strings are the classic example.
- Series: one break stops allThe great weakness of series is that one break stops everything: unscrew any bulb in a series circuit and the loop breaks at once, the other bulb going dark immediately, because the only path is cut and the current has nowhere to go. One burnt-out bulb in an old Christmas string darkens the whole set, and repairs mean testing them one by one, which is slow. This is exactly why household wiring does not use series.
- Parallel: many branchesParallel places components between the same two junction points, forming several branches: the current splits at the junction, each branch carrying one bulb, and every branch receives the battery's full voltage, so each bulb shines as if it had the battery alone. Household wiring is entirely parallel precisely for this feature — appliances on different branches do not affect one another and can be switched independently.
- Parallel: one break, rest stay onThe strength of parallel is independent branches: unscrew one bulb in a parallel circuit and the other keeps shining, because the current simply takes the branch still connected and the source is unaffected. At home, one dead lamp leaves the other lights and appliances working; an empty wall socket never blocks the others — all thanks to parallel. Such reliability is exactly what modern circuit design aims for.
- Comparing brightnessConnect the same battery to different arrangements and brightness tells them apart at once: a single bulb wired straight to the battery is brightest; two in parallel each receive the full voltage and stay near normal brightness; two in series share the voltage evenly and are clearly dimmer. The more bulbs in series, the less voltage each receives and the dimmer the string. This comparison experiment shows the difference between the two connection types directly — worth doing by hand.
- Everyday examplesTo judge a connection, count how many paths the current has: home lights, TV and fridge are all in parallel — switched independently, one fault affects no others; old-style Christmas lights were in series, so one dead bulb darkened the string. Car headlamps are also parallel: when one side burns out the other stays lit, keeping night driving safe. Parallel is evidently the reliable, flexible choice of modern life, while series appears only in special cases.
4Diagrams Diagrams
5Worked example Example
Example: an old string of Christmas lights has 10 identical bulbs in series. Why is each bulb quite dim, and what happens if one burns out?
- A series circuit offers one single path, so the same current passes through all 10 bulbs in turn.
- The battery voltage is shared among the 10 bulbs — each gets about one tenth.
- With so little voltage each bulb glows dimly.
- If one bulb burns out the loop is broken and the whole string goes dark.
- Answer: A series circuit has one single path, so the same current passes through all 10 bulbs in turn; the battery voltage is shared evenly, leaving each bulb only about one tenth, which is why they glow far below normal. If one bulb burns out, the loop breaks, no current can pass and the whole string goes dark. To keep the bulbs independent, a parallel connection should be used instead.
6Common mistakes Mistakes
7Quick check Quick check
Q1How many paths does the current have in a series circuit?
Q2In a parallel circuit, what happens to the other bulbs if one is removed?
Q3With the same battery, which is brighter — two bulbs in series or two in parallel?
Q4Which connection do home appliances use, and why?
Q5One dead bulb kills the whole string of old Christmas lights. What connection is that?
8Recap Recap
- Series: one path — one break stops all, and bulbs are dimmer.
- Parallel: branches — one break leaves the rest on, each bulb at normal brightness.
- In series the battery voltage is shared among the bulbs.
- Household wiring is parallel so appliances switch independently.
- To classify, count the current paths: one means series, a split means parallel.