In series circuits potential diference (posh name for voltage) is......SHARED.
The PD round a circuit always adds up to the PD across a battery.
This is because the total work done by a charge on a component must equal the total work done on a charge by the battery.
In series circuits current is the SAME everywhere
This is because the total current is determined by the total PD across a battery and the total resistance of the circuit.
In series resistance ADDS UP!
In series, the total resistance is the sum of the resistors.
This means that two or more resistors in series is more effective than just one because the battery has to push the charges through two resistors.
The bigger the total resistance of a component the greater its share of total PD. This is because more work is done by the charge as it moves through a large resistance.
If the resistance of one component changes (LDR of thermistor) then the resistance of the other components changes too.
In series cell voltages add up!
This is because as each charge moves through the cells it revceives a push from each of them.
(Cell voltages do not add up in parallel)
In series cell current doesn't add up!
The current would just be the same as if there was only one cell in the circuit.
(Cell current adds up in parallel. However the current through each cell is less because they add up to make the total current).