Series Circuits (Oxford AQA IGCSE Combined Science Double Award)

Series Circuit

• There are two ways of joining electrical components:

  • In series

  • In parallel

• Some circuits include both series and parallel parts

• For components connected in series:

  • the combined resistance is the sum of the resistance of each component

  • the current is the same in each component

  • the total potential difference of the power supply is shared between the components

  • The combined voltage of several sources in series is their sum

Current in series

• In a series circuit, the current is the same value at any point

  • So all components have the same current

  • The number of electrons per second that pass through one part of the circuit is the same number that passes through any other part

Current is the same

• The amount of current flowing in a series circuit depends on:

  • The voltage of the power source

  • The total resistance of the components

  • This is Ohm's law, but applied to the circuit as a whole

• Increasing the voltage of the power source drives more current around the circuit

  • So, decreasing the voltage of the power source reduces the current

• Increasing the number of components in the circuit increases the total resistance

  • Hence less current flows through the circuit

Increasing the voltage and number of components

Voltage in series

• The total potential difference of the power supply is shared between the components

Voltage is shared

Resistance in series

• When two or more resistors are connected in series, the total resistance is equal to the sum of their individual resistances

• For two resistors of resistance R₁ and R₂, the total resistance can be calculated using the equation:

• Where:

  •  R is the total resistance, in ohms (Ω)

• Increasing the number of resistors increases the overall resistance

  • The charge now has more resistors to pass through

Resistance is increased