# 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.