Capacitance · A Level Physics 9702 Simulation

About this lab: Capacitance

Interactive simulation for Cambridge A Level Physics 9702 topic 19 Capacitance: C = Q/V with a live Q-V graph and up to three capacitors in series or parallel with the charge and p.d. on each, the energy stored as the area under the V-Q graph with W = ½QV = ½CV² and the half lost in charging, discharge through a resistor with the exponential V, Q and I curves, the time constant RC, the ln V plot and the charge as the area under I-t, plus charging as an extra.

Charge stored per volt, capacitors in series and parallel, the energy in a charged capacitor, and the exponential discharge through a resistor

Capacitance is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 19 Capacitance). 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 4 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

19.1 Capacitors and capacitance: Capacitance: C = Q ÷ V; Capacitors in series and parallel: derivations. Lessons: Capacitors and capacitance.
19.2 Energy stored in a capacitor: Area under the V-Q graph; W = ½QV = ½CV². Lessons: Energy stored in a capacitor.
19.3 Discharging a capacitor: V, Q, and I against time during discharge; Time constant: τ = RC; Exponential decay: x = x₀ e^(−t/RC). Lessons: Discharging a capacitor.

Full syllabus map: A Level Physics 9702 topic 19.

How to use this simulation

1. Capacitance and combinations.
2. Energy stored.
3. Discharging.
4. Charging (extra).
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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