Force per unit mass
Field magnitude
At B
A radial gravitational field
Outwards is positive →Energy per unit mass
Potential
At B
Click or drag on either graph to move B. Use the sliders for keyboard control. Axes stay fixed as the points move; changing the source or plotted quantity rescales them.
Connect the graphs
Read the values at A and B
| Quantity | At A | At B |
|---|
Pause & apply
Can you read the field?
Six short checks. These examples have their own values, independent of the lab.
Choose an answer to see the reasoning.
Model assumptions & teaching notes
What the model represents
Radial models use a point source, or the external field of a spherically symmetric source. Here r is measured from its centre, not its surface. We show 1–10 m; the point-source equations are undefined at r = 0. These graphs do not describe the inside of a planet or conductor.
For radial fields, V = 0 at infinity. Curves approach zero without reaching it at any finite distance. Parallel plates use an ideal uniform field over 0–10 m, ignoring edge effects, with V = 0 at the right plate.
From graphs to exam answers
First distinguish field (force per kg or C) from potential (energy per kg or C). Then connect a tangent to the field at one point, and a signed area to a potential difference. The work view multiplies by the test mass or charge to show force and potential energy.
Simple source values make the arithmetic visible: initially GM = 100 m³ s⁻² or k|Q| = 100 V m. Test bodies do not alter the source. Work by an external agent assumes slow movement with no change in kinetic energy.
Curriculum: AQA 7408 §3.7.2–3.7.3; OCR A H556 §5.4.2, §5.4.4 and §6.2.2–6.2.4. AQA specification ↗ · OCR A specification ↗