Electric fields

About this lab: Electric fields

Field patterns of a point charge, a dipole, two like charges and parallel plates with a draggable test charge showing the force F = qE and how it reverses for a negative charge, a uniform field E = V/d between plates deflecting an electron, proton or alpha particle along a parabola with its deflection and exit angle, Coulomb's law with equal and opposite forces, an inverse-square check and a charged sphere acting as a point charge, the radial field of a point charge and a charged conducting sphere plus the vector addition of two fields and the neutral point, and electric potential with equipotentials, W = qΔV and E = −dV/dr, potentials adding as scalars around a pair of charges.

Field lines and a test charge, a charged particle fired between parallel plates, Coulomb's law, the inverse-square field of a point charge, and potential with its equipotentials

Electric fields is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 18 Electric fields). The course is assessed in Paper 1 (multiple choice), Paper 2 (AS structured), Paper 3 (advanced practical), Paper 4 (A Level structured) and Paper 5 (planning, analysis and evaluation). There are 5 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

• 18.1 Electric fields and field lines: Electric field as force per unit positive charge; F = qE; Representing E-fields with field lines. Lessons: Electric fields and field lines.
• 18.2 Uniform electric fields: E = ΔV ÷ Δd for parallel plates; Motion of charged particles in uniform fields. Lessons: Uniform electric fields.
• 18.3 Electric force between point charges: Spherical conductors as point charges at the centre; Coulomb's law: F = Q₁Q₂ ÷ (4πε₀r²). Lessons: Coulomb’s law.
• 18.4 Electric field of a point charge: E = Q ÷ (4πε₀r²). Lessons: Electric field of a point charge.
• 18.5 Electric potential: Definition: work done per unit positive charge from infinity; E-field as the negative gradient of potential; V = Q ÷ (4πε₀r) and Ep = Qq ÷ (4πε₀r). Lessons: Electric potential.

Full syllabus map: A Level Physics 9702 topic 18.

How to use this simulation

1. 1. Fields and field lines.
2. 2. Uniform fields.
3. 3. Coulomb’s law.
4. 4. Field of a point charge.
5. 5. Electric potential.
6. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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