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.