Draw and interpret practical circuit diagrams
Recognise standard component symbols and translate a described circuit into a clear labelled diagram.
Section 10 · D.C. circuits
AS Level; Cambridge International Physics 9702, 2025–2027 syllabus, Topic 10. These original circuit diagrams and calculations are study aids; full timed assessment, supervised practical competence and human subject-teacher review remain outstanding.
Before you begin
- Use current, potential difference, resistance, energy and charge with consistent circuit directions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
How is an ammeter connected to measure branch current?
What you will learn
- Recall the syllabus circuit symbols
- Draw and interpret circuit diagrams with those symbols
- Place meters in the branch and orientation used for their measurement
Symbols make circuit connections unambiguous
Circuit diagrams use standard symbols for cells and batteries, switches, resistors, variable resistors, lamps, diodes, thermistors, light-dependent resistors, ammeters and voltmeters. A line represents a conducting connection; crossings and junctions must be drawn clearly so the intended connections are visible.
An ammeter measures current through a branch and is placed in series. A voltmeter measures potential difference between two points and is connected in parallel across the component. Follow the syllabus symbol convention in a drawn answer rather than using a picture of the physical component.
Translate a description into a connected circuit
Start by identifying the source and the complete loop, then add components in the described order. Put series components on the same branch and draw parallel branches with both ends connected to the correct junctions.
Label known values and the quantity to be measured. A circuit can contain the right symbols but still be wrong if a branch is open, a meter is placed in the wrong connection, or a component is short-circuited by a wire.
Pause and explain
Where does a voltmeter connect to measure a resistor's potential difference?
Worked example
Describe how to add an ammeter to measure the current through a lamp and a voltmeter to measure its potential difference.
Show the worked solution
- Break the lamp branch and place the ammeter in series so the same branch current passes through it.
- Connect the voltmeter across the two terminals of the lamp.
- Keep a complete source–lamp circuit and do not connect the voltmeter as a series element.
Answer Place the ammeter in series with the lamp and the voltmeter in parallel across it.
Try a topic test
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.
A circuit has one cell, a switch and a lamp in one loop. State the order of connections and add an ammeter to measure lamp current.
Give me a hint
Keep the source, switch and lamp in one closed series loop.
Compare my reasoning
- Draw the cell, switch and lamp in the same loop.
- Break the lamp branch and insert the ammeter in series.
- Check the path is complete when the switch is closed.
Cell, switch, ammeter and lamp are connected in one series loop, with the ammeter measuring the lamp-branch current.
Look for these in your work
- Components placed in one loop
- Ammeter in series
- Complete path checked
A voltmeter is intended to measure across a diode. Describe its two connection points and the diode's position in the circuit.
Give me a hint
Compare the meter's terminals with the two diode terminals.
Compare my reasoning
- Connect one voltmeter terminal to each diode terminal.
- This places the voltmeter in parallel across the diode.
- Keep the diode in its circuit branch with the source and any required series component.
The voltmeter connects across the two diode terminals while the diode remains in its branch.
Look for these in your work
- Both component terminals identified
- Parallel connection stated
- Diode branch retained
A diagram shows an ammeter drawn across a lamp and a voltmeter in series with it. Identify both faults and correct them.
Give me a hint
Match each meter connection with the physical quantity it is designed to measure.
Compare my reasoning
- The ammeter is across the lamp, but it must be in series in the lamp branch.
- The voltmeter is in series, but it must connect across the lamp terminals.
- Redraw so the lamp-branch current passes through the ammeter and the voltmeter bridges the lamp.
Swap the meter arrangements: put the ammeter in series with the lamp and the voltmeter in parallel across it.
Look for these in your work
- Both wrong connections identified
- Correct meter arrangements stated
- Measurement purpose linked
Common mistakes
- Placing a voltmeter in series
- Placing an ammeter in parallel across a source or component
- Drawing disconnected branches that appear to join but do not
What can you explain now?
How is an ammeter connected to measure branch current?
Compare with the explanation
In series in that branch
The branch current passes through the meter.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Why does a voltmeter bridge a component while an ammeter sits inside its branch?
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.