Electric Field Lab
Explore superposition from point charges and measure the electric field at a probe.
Explore the lab
What you can explore
- Charge signs and positions
Configure up to four point charges to see field arrows point away from positive and toward negative charges.
- Field superposition
Move the probe and compare each active charge contribution with the resultant Ex and Ey.
- Test-charge force
Enable a test charge and change its sign to compare qtestE with the measured electric field.
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The model
Formula and underlying model
Eᵢ = kqᵢ(r − rᵢ)/|r − rᵢ|³; Etotal = ΣEᵢ
|E| = k|q|/d² (single charge); Ftest = qtest Etotal- qᵢ, qtest
- Source and test charges; UI uses µC (1 µC = 10⁻⁶ C) (C in formula)
- r, rᵢ, d
- Probe position, charge position and separation (m)
- E
- Electric field vector (N/C)
- Ftest
- Force on the test charge (N)
- k
- Coulomb constant = 8.9875517923×10⁹ (N·m²/C²)
Ideal point charges in a 2D view of the field. Coincident/very close probes are guarded; normalized display arrows do not represent equal true magnitudes. Field lines and equipotentials are not implemented.
The experiment
How it works
Configure charges
Set charge magnitudes, signs and positions or choose a preset.
Sample at the probe
Move its x/y coordinates to calculate each field contribution.
Compare the resultant
Inspect component sums and optional test-charge force.
Learning outcomes
What you’ll learn
- Explain electric-field direction for each charge sign.
- Add field contributions using vector superposition.
- Distinguish electric field from force on a test charge.
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Explore lab →Ready to experiment?
Explore Electric Field interactively
Open the lab, adjust the parameters, and see the results change in real time.