Physics · KS3 and GCSE · Interactive lesson
Electric circuits, current, power and energy
Trace current through series and parallel circuits. Explore voltage and resistance, then connect appliance power to energy use.
Choose your view
Explore an interactive example, then try the questions at your own pace.
KS3 / GCSE · start with the idea
By the end of this lesson: Trace current around a complete circuit and compare routes.
The interactive diagram and controls are in Stage 2, “Explore one example”. Read the idea here, then try it next.
- In series, there is one route around the circuit.
- In parallel, the route splits into branches, then rejoins.
- Current tells us how much electric charge flows each second. It is not used up by a resistor.
Useful starting points
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What do the words mean?
- Ammeter
- A meter used to measure electric current.
- Resistor
- A component that resists the flow of charge. The rectangles in the diagram are resistors.
- A (ampere)
- The unit for current: how much charge flows each second.
- V (volt)
- The unit for voltage, also called potential difference.
- Ω (ohm)
- The unit for resistance.
Change the example
This is the lesson example. Your practice question uses its own numbers.
Something to try
Switch between series and parallel. Follow one complete route from one battery terminal to the other.
Notice what changes
How particle motion works +
Starts paused. Press Play, then add energy to see the warmer particles move faster.
Particles keep the same size. Liquid particles move around; solid particles vibrate around fixed positions. This is a simplified model, with the change in motion exaggerated to make it easier to see.
About the playback +
About this model
Trace from one battery connection, through the resistors, to the other connection. In this model the battery voltage stays steady and wire resistance is treated as zero.
More about this diagram
Still picture. Play particle motion in Stage 2.
Series: one route; the same current throughout.
Still picture of the example from Stage 2. Use the back arrow to change it.
Work through it
Starting example: read the steps below
- Start at one battery terminal (connection point).
- There is one route, through both resistors.
- The same current passes through each resistor.
- Current is not used up. Energy is transferred in the resistors.
Try on your own
Your turn. No rush.
Question 1
In a series circuit with two resistors, how many separate routes are there through the resistors?
About these questions
Questions appear in a mixed order. Work at your own pace and stop whenever you like.
These questions use their own numbers, separate from the lesson example. You can stop whenever you like. Answers last for this visit to the page.
A good place to pause
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Can you trace the current routes and explain what happens at a junction?
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Notes for parents and tutors
These lessons cover selected KS3 and GCSE ideas for England; they are not a complete course. The level notes explain where GCSE methods or optional extensions begin. Maurice can help you choose material for your course and exam board.
The content draws on the DfE Maths curriculum, DfE Science curriculum and AQA GCSE Physics specification. Level labels are guidance, not exam-board endorsements. For AQA Radioactivity, calculating net decline as a ratio is Higher-tier work. Net means the overall change; ask Maurice whether this extension is relevant to your course. Explanations and practice were reviewed during development on 21 October 2026; Maurice should check their fit before assigning work.
Topic labels and your lesson-view preference are saved in this browser. This tab also remembers the last lesson stage, so you can choose to continue there. If you choose revision, selected activities and suggested revisit dates are saved here too. Recent question codes are also kept to reduce repeats. Reflection notes are saved automatically per topic when you type them; you can delete a note in the recap. They stay in this browser and are visible to other people using it. Practice answers and enquiry details are not saved. Clearing browser data removes the labels.