Circuit Combinations
One loop or many branches? Learn the rules for series and parallel circuits — how current, potential difference and resistance behave in each — and never mix them up again.
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Circuit Combinations 🔌
There are two ways to wire components together: in a single loop (**series**) or on separate branches (**parallel**). The two behave very differently. Learn how **current**, **potential difference** and **resistance** act in each, and you can read any circuit.
Series circuits ➿
In a **series** circuit, everything sits in **one loop**: • The **current** is the **same** at every point. • The **potential difference** is **shared** between the components (it adds up to the supply p.d.). • The **total resistance** is the **sum** of the resistances: R = R₁ + R₂ + ...
Total resistance in series
An interactive activity.
Series facts
Pick the TWO statements that are true for a SERIES circuit.
- The current is the same at every point
- The total resistance is the sum of the resistors
- The potential difference is the same across every component
- The current splits between separate branches
Parallel circuits 🔀
In a **parallel** circuit, components sit on **separate branches**: • The **potential difference** across each branch is the **same** (equal to the supply). • The **current splits** between the branches, and the branch currents add back up to the total. • The **total resistance decreases** — it is **less than the smallest** single resistor.
Total resistance in parallel
An interactive activity.
P.d. in parallel
In a parallel circuit, how does the potential difference across each branch compare?
- It is the same across every branch (equal to the supply p.d.)
- It is shared out between the branches
- It is zero in every branch
- It is largest in the first branch
Match each case to its behaviour
- Current in a series circuit
- Current in a parallel circuit
- Potential difference in a series circuit
- Potential difference in a parallel circuit
- The same at every point
- Splits between the branches
- Shared between the components
- The same across every branch
Adding more resistors 📉
The two arrangements pull total resistance in **opposite** directions: • Add a resistor in **series** → total resistance **increases** (the current has more to get through). • Add a resistor in **parallel** → total resistance **decreases** (the current gets another route, so more can flow).
Adding in parallel
What happens to the total resistance of a circuit when you add another resistor in PARALLEL?
- It decreases — the total becomes less than the smallest resistor
- It increases
- It stays the same
- It becomes infinite
Order the method
An interactive activity.
The circuit rules
In a series circuit the current is the _____ everywhere, and the total resistance is the _____ of the resistors. In a parallel circuit the potential difference is the same across every _____.