Series Circuits-All or Nothing

• In series circuits, the different components are connected in a line, end to end, between the +ve and -ve of the power supply(except for voltmeters, which are always connected in parallel, but they don’t count as part of the circuit).

• If you remove or disconnect one component, the circuit is broken and they all stop. This is generally not very handy, and in practice very few things are connected in series

• You can use the following rules to design series circuits to measure quantities and test components

Potential Difference is Shared

In series circuits the total pd of the supply is shared between the various components. So the potential difference round a series circuit always add up to equal the source pd:

V(total) = V1 + V2 +…

Current is the same everywhere

In series circuits the same current flows through all components: R(total) = R1 + R2

The size of the current is determined by the total pd of the cells and the total resistance of the circuit

I = V / R

Resistance Adds Up

In series circuits the total resistance of two components is just the sum of their resistance. This is because by adding a resistor in series, the two resistors have to share the total pd. The potential difference across each resistor is lower, so the current through each resistor is also lower. In a series circuit, the current is the same everywhere so the total current in the circuit is reduced when a resistor is added. This means the total resistance of the circuit increases. The bigger a component’s resistance, the bigger its share of the total potential difference

Cell Potential Difference Adds Up

There is a bigger pd when more cells are in series, if they’re all connected the same way. For example when two cells with a potential difference of 1.5V are connected in series they supply 3V between them.