Series circuits
- Components are connected one after another in a single loop.
- The current is the same through each component.
- The total potential difference of the supply is shared between the components.
- The total resistance is the sum of the individual resistances: R_total = R₁ + R₂.
Parallel circuits
- Components are connected on separate branches.
- The potential difference across each branch is the same (equal to the supply pd).
- The total current is the sum of the currents through the separate branches.
- The total resistance of two resistors in parallel is less than the resistance of the smaller one.
Why resistance changes
- Adding resistors in series increases the total resistance, because the charge has to pass through each resistor in turn.
- Adding resistors in parallel decreases the total resistance, because there are more paths for the charge to flow through.
Solving series problems
- Find the total resistance, then the current: I = V ÷ R_total.
- Then find the pd across each resistor: V = I R.
- Check: the pds across the resistors add up to the supply pd.
Key terms
- Series circuit
- A circuit where components are connected in one loop.
- Parallel circuit
- A circuit where components are connected on separate branches.
- Branch
- A separate path in a parallel circuit.
- Total resistance
- The combined resistance of all the components in a circuit.
- Junction
- A point where a circuit splits or joins.