3.2 Potential Difference

Potential Difference

• A cell makes 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

• The potential difference is defined as the work done per unit charge and is measured in units of volts (V)

Measuring Voltage

• Potential difference (or voltage) is measured using a voltmeter
• A voltmeter is always set up in parallel to (also called 'across') the component being measured
  • Potential difference across components in parallel is always the same due to conservation of energy

Potential difference can be measured by connecting a voltmeter in parallel between two points in a circuit

Step 1: Write down the known quantities

• • Potential difference, V = 10 V
  • Charge, Q = 2 C

Step 2: Write down the equation relating potential difference, work done and charge

Step 3: Rearrange the equation to make work done the subject

Step 4: Substitute in the values and calculate W