Potential Difference (Cambridge (CIE) AS Physics)

Defining potential difference

• 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.

Calculating potential difference

• 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)