Voltage in Series & Parallel Circuits (WJEC GCSE Physics): Revision Note

Voltage in Series & Parallel Circuits

Voltage

• The terminals a cell make one end of the circuit positive and the other negative

• This creates a voltage across the circuit

  • Voltage is also sometimes called potential difference (or p.d.)

• The voltage across the circuit drives the current to flow

• Energy is transferred from the power supply to the components

• Voltage has the symbol V

Voltage in Series Circuits

• In a series circuit, the voltage is shared between the components

• The sum of voltages across the individual components is equal to the total voltage of the power supply

• If the components have equal resistance, then the voltage is shared equally

Voltage in a Series Circuit

In a series circuit, the components share the voltage of the power supply

Voltage in Parallel Circuits

• In a parallel circuit, the voltage across each branch is the same

  • If components are placed in series within a branch, then the voltage is split across the components within the branch in accordance with the rules of voltage in series

Voltage in Parallel Circuits

Lamps connected in parallel have the same voltage as that of the power supply

• Advantages of parallel circuits:

  • If one component in one branch stops working, components in other branches will still work

  • The voltage is the same in all branches, therefore bulbs shine brighter when connected in parallel (they have to share the energy transferred from the power supply when positioned in series)

  • It is easier to add new loops to an existing circuit (for example household lighting circuits)

  • A fuse can be added to each loop making the circuit safer overall

Measuring Voltage

• Voltage (or potential difference) is measured using a voltmeter

  • This is described as measuring voltage 'across' the component

• The unit for voltage is volts, which has the symbol V

• A voltmeter is always set up in parallel to the component being measured

A Voltmeter in Parallel to the Component Being Measured

Voltage can be measured by connecting a voltmeter in parallel between two points in a circuit. Here, the voltmeter is measuring the voltage across the resistor