Potential Difference (Edexcel GCSE Physics)

Potential Difference

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

• This sets up a potential difference across the circuit

  • This is sometimes known as the voltage

• Potential difference is defined as:

  The amount of energy transferred per unit of charge passing through the terminals

• This means that one volt (the unit of potential difference) is equivalent to one joule (the unit of energy) per coulomb (the unit of charge):

1 V = 1 J / C

• Potential difference can be calculated using the equation below:

• Where:

  • V = potential difference, measured in volts (V)

  • E = energy transferred, measured in joules (J)

  • Q = charge moved, measured in coulombs (C)

• The equation for potential difference can be rearranged using the formula triangle below:

Energy, charge, potential difference formula triangle

Voltmeters

• Potential difference (or voltage) is measured using a voltmeter

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

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

Potential difference (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