Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Use the equation: energy transferred (joule, J) = current (ampere, A) ×…
Full specification wording
Topic 10 – Electricity and circuits: 10.27 Use the equation: energy transferred (joule, J) = current (ampere, A) × potential difference (volt, V) × time (second, s)
The energy transferred by an electrical device equals current multiplied by potential difference multiplied by time: E = I × V × t.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 25 of 39
Study notes
From the checked teaching notes for this specification point.
The idea
The energy transferred by an electrical device equals current multiplied by potential difference multiplied by time: E = I × V × t. Current is in amperes, potential difference in volts and time in seconds, so the energy comes out in joules.
For example: A current of 2 A flowing through a component with a potential difference of 6 V for 30 s transfers 2 × 6 × 30 = 360 J. Convert time to seconds before substituting (3 minutes = 180 s) and rearrange for the unknown when the question asks for current, potential difference or time rather than energy.
What earns the marks
- Selects the relationship energy transferred = current × potential difference × time.
- Substitutes current in amperes, potential difference in volts and time in seconds into the equation.
- Calculates energy transferred in joules from the product of the three quantities.
- Rearranges the equation to find current, potential difference or time when one of these is the unknown.
Common mistakes and how to put them right
Enters time in minutes rather than seconds.
Put it right: Convert to seconds before multiplying.
Adds the three quantities instead of multiplying them.
Put it right: Multiply current, potential difference and time together.
Uses the wrong unit for the answer.
Put it right: State the energy transferred in joules.
Exam tips
- Write the equation first, then substitute values with their units.
- Convert any time given in minutes to seconds before calculating.
- Check the size of the answer against the units to catch a slip.
Try the lesson
The start of the Topic 10 – Electricity and circuits: 10.27 Use the equation: energy transferred (joule, J) = current (ampere, A) × potential difference (volt, V) × time (second, s) lesson, made from checked teaching notes for this specification point.
Have a go first
A current of 2 A flows through a lamp when the potential difference across it is 12 V. The lamp is switched on for 5 s. Calculate the energy transferred to the lamp.
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