AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Energy transfers in everyday appliances: potential difference, V, in volts, V
Potential difference, symbol V, is the energy transferred per unit charge passing between two points in a circuit, measured in volts, symbol V. One volt equals one joule per coulomb, so a 12 V…
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Potential difference, symbol V, is the energy transferred per unit charge passing between two points in a circuit, measured in volts, symbol V. One volt equals one joule per coulomb, so a 12 V battery transfers 12 J of energy to each coulomb of charge that it drives around the circuit. In everyday appliances, the potential difference of the mains supply, about 230 V in the UK, determines how much energy each coulomb carries, so a mains lamp transfers far more energy per coulomb than a 1.5 V cell lamp.
What earns the marks
- State that potential difference is the energy transferred per unit charge between two points in a circuit.
- Give the unit of potential difference as the volt, symbol V, and relate one volt to one joule per coulomb.
- Identify the symbol V as representing potential difference in equations such as E = QV and P = VI.
- Describe how to measure potential difference using a voltmeter connected in parallel across a component or supply.
- Interpret a stated potential difference, for example 230 V mains or 1.5 V cell, as the energy in joules transferred per coulomb of charge.
- Use potential difference with current and time to calculate energy transferred by an everyday appliance.
Common mistakes and how to put them right
Confusing potential difference with current.
Put it right by linking V to joules per coulomb.
Connecting a voltmeter in series with a component.
Put it right: A voltmeter must be connected in parallel across the component so that it compares the energy at the two points; correct the circuit diagram accordingly.
Writing the unit as V without distinguishing quantity and unit.
Put it right by stating both clearly, for example potential difference V measured in volts, V.
Exam tips
- When a question gives a potential difference, write down the value with its unit before substituting it into any equation.
- Check whether the question asks for a definition, a measurement method or a calculation, and tailor your answer to that command word.
- In circuit questions, sketch the voltmeter in parallel across the correct component before doing any arithmetic.
Try the lesson
The start of the Energy transfers in everyday appliances: potential difference, V, in volts, V lesson, made from checked teaching notes for this specification point.
Have a go first
A battery is labelled with a potential difference of 6 V. What is the unit of potential difference?
Listen
Potential difference, symbol V, is the energy transferred per unit charge passing between two points in a circuit, measured in volts, symbol V. One volt equals one joule per coulomb, so a 12 V battery transfers 12 J of energy to each coulomb of charge that it drives around the circuit. In everyday appliances, the potential difference of the mains supply, about 230 V in the UK, determines how much energy each coulomb carries, so a mains lamp transfers far more energy per coulomb than a 1.5 V cell lamp. A strong answer earns marks for these points. State that potential difference is the energy transferred per unit charge between two points in a circuit. Give the unit of potential difference as the volt, symbol V, and relate one volt to one joule per coulomb. Identify the symbol V as representing potential difference in equations such as E = QV and P = VI. Describe how to measure potential difference using a voltmeter connected in parallel across a component or supply. A common slip: Confusing potential difference with current: current is the rate of flow of charge in amperes, whereas potential difference is energy transferred per unit charge in volts. Instead, linking V to joules per coulomb. Exam tip: When a question gives a potential difference, write down the value with its unit before substituting it into any equation.
Key words
Say what each word means before you turn the card.
Potential difference
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Volt
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Voltmeter
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Mains supply
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See every definition
- Potential difference
- The energy transferred per unit charge passing between two points in a circuit, measured in volts, symbol V.
- Volt
- The unit of potential difference, symbol V, where one volt equals one joule per coulomb.
- Voltmeter
- An instrument connected in parallel across a component or supply to measure potential difference, read in volts.
- Mains supply
- A supply with a potential difference of about 230 V in the UK, determining how much energy each coulomb carries.
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