Identify lamps motors and bells as circuit outputs
Draw recognizable output symbols and explain the different energy transfers they provide.
Section P4.2 · Electrical circuits
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Trace a complete load path.
- Identify energy transfer without charge consumption.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What happens to charge passing through an ordinary lamp in a series path?
What you will learn
- Draw lamp, motor and bell symbols.
- Distinguish useful light, motion and sound outputs.
Read the output symbols
A filament lamp symbol is a circle with a cross inside. Current heats its filament and it emits light; heating of the surroundings also occurs. A motor symbol commonly uses a circle containing M. With a suitable supply it provides mechanical movement; operating speed and load are not determined solely by the symbol.
A bell uses an identifiable bell-shaped symbol or a labelled bell representation. A typical electromagnetic bell converts electrical input into repeated mechanical motion and sound. The visible symbol represents the circuit component rather than a full internal mechanism. Distinguish it from a motor by its label and output purpose.
Describe useful and other transfers
A lamp is normally selected for light, a motor for mechanical output, and a bell for audible sound. Each may also transfer energy by heating; actual efficiency requires supplied input and useful-output data. A label alone does not prove an ideal loss-free device.
Put an output in a complete conducting path with an appropriate source. Draw an actual lamp circle/cross, M circle and bell symbol rather than relying on household pictures. If a circuit interruption makes current zero, these ordinary electrically driven outputs cannot sustain their usual powered action in that model. Charge is not consumed at the output.
Sources for this lesson
Pause and explain
A bell is powered by a cell. Which account is appropriate?
Worked example
Identify the principal intended outputs of a lamp, motor and bell.
Show the worked solution
- A lamp provides light.
- A motor provides mechanical movement.
- A bell provides sound through its mechanism.
Answer Lamp: light; motor: mechanical movement; bell: sound.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Draw a lamp symbol and a motor symbol, then label each intended output.
Give me a hint
Use circle/cross and circle/M conventions.
Compare my reasoning
- Draw a circle with a cross for the lamp.
- Draw a circle containing M for the motor.
- Label light and mechanical movement respectively.
Lamp circle/cross → light; motor circle/M → mechanical movement.
Look for these in your work
- Draw both symbols.
- Name distinct outputs.
Draw a labelled bell in a closed cell-and-switch circuit and describe its intended action.
Give me a hint
Use a recognizable bell representation and a complete return path.
Compare my reasoning
- Draw the cell and a closed switch.
- Put the labelled bell symbol in the loop.
- Explain electrical input causing the bell mechanism to produce sound.
A bell in a complete switched path provides audible output through mechanical action.
Look for these in your work
- Retain the return wire.
- Explain the sound-producing role.
A motor diagram gives no input power, efficiency or load. A learner assigns its exact speed and says all input becomes useful motion. Assess the claims.
Give me a hint
A symbol identifies a component but is not its full operating specification.
Compare my reasoning
- M identifies the motor.
- Exact speed requires operating and load information.
- Useful-output fraction needs efficiency or measured input/output data.
Neither exact speed nor perfect efficiency follows from the motor symbol alone.
Look for these in your work
- Keep component identity.
- Identify the missing operating data.
Common mistakes
- M identifies a motor, not an ammeter.
- Useful output is not the whole input energy.
- A bell diagram need not show every internal part.
What can you explain now?
Which symbol commonly identifies a motor?
Compare with the explanation
A circle containing M.
The M label distinguishes the motor from other circular device symbols.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Draw lamp, motor and bell symbols and explain their useful outputs without assuming ideal efficiency.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.