Recognize a three terminal potential divider symbol
Distinguish a variable track and wiper from a two-terminal adjustable resistor before studying divider calculations.
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
- Recognize a variable resistor.
- Describe p.d. between two points.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does a voltmeter need to measure p.d.?
What you will learn
- Draw the track endpoints and wiper.
- Identify the intended output terminal pair qualitatively.
Identify the third terminal
A variable potential divider uses a resistive track with two end terminals and a sliding contact called the wiper. Its diagram shows a resistor track and an arrow contact connected to a third terminal. The supply is applied across the track ends; an output can be taken between the wiper and a specified end.
A two-terminal variable resistor uses a selected portion of the track to change path resistance. A three-terminal divider uses both track sections to choose an output p.d. The presence of an arrow does not alone establish which arrangement is wired: count and trace the connected terminals.
Describe its purpose without a numerical model
The wiper position selects the contact along the track and lets the output vary. State which end is the output reference. The Core symbol requirement is to recognize, draw and interpret this component; the detailed variable-divider action and resistance–voltage calculations are separately labelled Supplement lessons.
Draw the source across the two ends and an output pair from the wiper and chosen end. Do not draw a wire that directly bypasses the track between the source terminals. The voltage response with an attached load depends on that load, so no exact numerical output follows from an unlabelled symbol.
Sources for this lesson
Pause and explain
Which wiring identifies a three-terminal divider?
Worked example
Identify the three connections in a divider diagram with a supply across its track and output from the wiper to the lower end.
Show the worked solution
- The track has upper and lower end terminals.
- The arrow contact has a separate wiper terminal.
- The output is defined between wiper and lower end.
Answer Two track-end supply terminals and a third wiper terminal; output wiper-to-lower end.
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.
Draw a variable divider track with both end terminals and a separate wiper terminal.
Give me a hint
Use a resistor track and an arrow that contacts the track.
Compare my reasoning
- Draw the two-terminal resistive track.
- Add the sliding-contact arrow into the track.
- Extend the arrow connection as the third terminal and label it wiper.
A track with two end terminals and a third arrow-contact wiper terminal.
Look for these in your work
- Show all three terminals.
- Use the contact rather than a floating arrow.
Add a supply across the track and mark output between wiper and lower end.
Give me a hint
Label the output as a pair, not an isolated point.
Compare my reasoning
- Connect supply terminals to opposite track ends.
- Identify the wiper terminal.
- Mark the output measurement from wiper to lower end.
Supply across track ends; output across wiper and lower end.
Look for these in your work
- Trace the source pair.
- Identify the output reference.
A student labels a two-connected-terminal adjustable resistor as a divider with an exact 3 V output, but no supply or output reference is shown. Assess the drawing.
Give me a hint
Count used terminals and identify what a voltage specification needs.
Compare my reasoning
- No three-terminal output arrangement is established.
- The source p.d. and output pair are missing.
- An exact output requires a defined circuit and operating data.
The drawing does not establish a three-terminal divider or an exact 3 V output.
Look for these in your work
- Inspect actual connections.
- Avoid an unprovided voltage.
Common mistakes
- Count three terminals rather than every arrow as a two-terminal resistor.
- Name the output reference end.
- Detailed divider action and equations are Supplement work.
What can you explain now?
What is the movable third contact called?
Compare with the explanation
The wiper.
Its position selects a point along the resistive track.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Draw the track, endpoints and wiper, and identify both output terminals before applying divider equations.
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.