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Physics 11–12 · Year 11

Mapping electric fields and equipotentials on conductive paper

Module 4: Electricity and Magnetism (Electrostatics)

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The idea

Field lines run from positive to negative electrodes, cross equipotential lines at right angles, and are closest where the potential changes fastest.

What you need

  • Carbon-coated conductive paper on a cork board, silver conductive ink or brass push-pin electrodes
  • 12 V DC supply, digital voltmeter with a probe, graph paper for the map
  • Electrode shapes: two points (dipole), two parallel strips (plates), a point and a strip

How to do it

  1. Draw two parallel strip electrodes 10 cm apart and connect them to 12 V.
  2. With the voltmeter negative lead on the 0 V strip, probe the paper to find points at 2, 4, 6, 8 and 10 V; join each set into an equipotential line.
  3. Draw field lines perpendicular to the equipotentials from the positive to the negative electrode.
  4. Repeat with two point electrodes to map a dipole and note where lines crowd.
  5. For the strips, plot V against distance from the 0 V strip; the gradient is the field strength E = V/d.

What you should see

Between the strips the equipotentials are evenly spaced straight lines and the field is uniform: 12 V over 0.10 m gives 120 V/m. Around the dipole the equipotentials are curved, crowd near the electrodes and the field lines bulge outward, matching the textbook pattern. The learner knows it worked when voltage against distance between the strips is a straight line within about 5 per cent, away from the ends of the strips.

What changes

What you change
position of the probe
What you measure
potential
What you keep the same
  • supply voltage
  • electrode geometry
  • same sheet

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • Field lines are real paths that charges follow; they show the force direction, and a moving charge's path can differ.
  • Potential and field are zero at the same places; at the midpoint of a dipole the potential is zero but the field is not, and midway between two equal like charges the field is zero but the potential is not.

Safety card

Low riskLearners carry it out

Hazards

  • 12 V supply only

Controls

  • low-voltage DC

Note

Record the activity in RiskAssess (https://www.riskassess.com.au/) and follow the Science ASSIST risk management information sheet (https://asta.edu.au/resource/ais-risk-management-and-risk-assessment/).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Physics Stage 6 Syllabus (2017), current: Year 11 until the end of 2026, Year 12 until Term 3 2027PH11-11PH11/12-5
  • Physics 11-12 Syllabus (2025), not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027, first HSC examination 2028PY-11-03PY-11WS-04
  • Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

  1. www.nsw.gov.au/sites/default/files/noindex/2025-03/physics-stage-6-syllabus-2017.docx
  2. education.nsw.gov.au/content/dam/main-education/teaching-and-learning/curriculum/key-learning-areas/science/media/documents/physics-s6-module-4-guide-electricity-and-magnetism.docx
  3. phet.colorado.edu/en/simulations/charges-and-fields
  4. curriculum.nsw.edu.au/learning-areas/science/physics-11-12-2025/outcomes

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