Potential Difference (CIE A Level Physics)

• A cell makes one end of the circuit positive and the other negative. This sets up a potential difference (p.d.) across the circuit
• The potential difference across a component in a circuit is defined as:

The energy transferred per unit charge flowing from one point to another

• Potential difference (sometimes called voltage) is measured in volts (V). One volt is the same as one joule per coulomb (J C^-1)
  • If a bulb has a potential difference of 3 V, every coulomb of charge passing through the bulb will transfer 3 J of energy to the bulb
• The potential difference of a power supply connected in series is always shared between the components in the circuit

Potential difference in a series circuit

The potential difference is the voltage across each component in a circuit

• Potential difference is measured using a voltmeter
• A voltmeter is always set up in parallel so that it can measure the difference in electrical potential on each side of the component
  • This is a measure of how much energy has been transferred to the component

Potential difference in a parallel circuit

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

• The potential difference is defined as the energy transferred per unit charge
• Another measure of energy transfer is work done
• Therefore, potential difference can also be defined as the work done per unit charge

• • V = potential difference (V)
  • W = work done (J)
  • Q = charge (C)