Components are connected end to end
All the current flows through all the components
Can only switch them all off at once
Potential difference is shared across the whole circuit
PD of power supply = sum of PD across each component
Current is the same through all parts of the circuit
Current at one point = current at any other point
Total Resistance is the sum of the resistance in each component
Resistance of two components is bigger than just one of them, because the charge has to push through both of them when flowing round the circuit