Electricity and d.c. circuits

About this lab: Electricity and d.c. circuits

Seven benches on a real circuit engine: charge carriers drifting to give I = nAvq, p.d. and the three forms of power, I-V characteristics of a metal, a filament lamp and a diode with R plotted against V, resistivity of a wire, e.m.f. and internal resistance with the V-I line and maximum power, Kirchhoff's laws in series, parallel and a two-cell two-loop circuit, and the potential divider and potentiometer null method.

Charge carriers, power, I-V characteristics, resistivity, internal resistance, Kirchhoff and the potentiometer

Electricity and d.c. circuits is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 9 Electricity; topic 10 D.C. circuits). 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 7 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

• 9.1 Electric current: Current as a flow of charge carriers; quantised charge; Q = It; Charge carrier density: I = Anvq. Lessons: Electric current.
• 9.2 Potential difference and power: P.D. as energy transferred per unit charge: V = W ÷ Q; Power: P = VI, P = I²R, P = V² ÷ R. Lessons: Potential difference and power.
• 9.3 Resistance and resistivity: Resistance: V = IR; I–V characteristics: conductor, diode, filament lamp; Ohm's law; Resistivity: R = ρL ÷ A; LDRs and thermistors (NTC). Lessons: Resistance and resistivity.
• 10.1 Practical circuits: Circuit symbols and drawing circuit diagrams; E.M.F. as energy per unit charge in a complete circuit; E.M.F. vs P.D. (energy considerations); Internal resistance and terminal P.D.. Lessons: E.M.F. and internal resistance.
• 10.2 Kirchhoff's laws: Kirchhoff's first law: conservation of charge; Kirchhoff's second law: conservation of energy; Deriving combined resistance: series and parallel; Solving circuit problems using Kirchhoff's laws. Lessons: Kirchhoff laws.
• 10.3 Potential dividers: The potential divider principle; The potentiometer for comparing P.D.s; Galvanometer and null methods; Thermistors and LDRs in potential divider circuits. Lessons: Potential dividers.

Full syllabus map: AS Level Physics 9702 topic 9 and AS Level Physics 9702 topic 10.

How to use this simulation

1. 1. Charge carriers, I = nAvq.
2. 2. P.d. and power.
3. 3. I-V characteristics.
4. 4. Resistivity.
5. 5. E.m.f. and internal resistance.
6. 6. Kirchhoff’s laws.
7. 7. Potential divider and potentiometer.
8. 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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