Circuit builder sim
The student drags real cells, lamps, resistors, meters and sensors onto a board, wires them with plug leads and sees the circuit work, then checks it as a circuit diagram.
D.C. circuits · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Each part behaves like the real apparatus, and the current in every branch is found from Kirchhoff's laws (nodal analysis) every time the circuit changes, in real time. In series the current is the same everywhere and the p.d. is shared in proportion to resistance (V = IR). In parallel each branch gets the same p.d. and the branch currents add up to the current in the main lead. A cell has emf 1.5 V and internal resistance 0.5 Ω, so its terminal p.d. falls as it delivers current: one lamp on one cell gets about 1.39 V and 0.23 A. A filament lamp's resistance rises as it heats, from about 2 Ω cold to about 8.3 Ω at its rated 2.5 V, 0.3 A. An LED conducts one way only, once the p.d. across it reaches about 1.9 V, and needs a series resistor (above 50 mA it burns out). The 1 A fuse melts when the current stays above 1 A (I²t heating: about 1 s at 1.5 A). An LDR's resistance falls in brighter light (10 kΩ in the darkened room to 200 Ω close to the lamp); an NTC thermistor's falls as it warms (10 kΩ at 25 °C, about 0.9 kΩ at 90 °C, with a 2 s lag). Ammeters (0.1 Ω) go in series and voltmeters (10 MΩ) in parallel; wired the other way they give the readings shown. Limits: cells do not run down, leads have no resistance, resistors are exact, and the lamp, fuse and LED fail at simple heating thresholds.
- Filament lamp: dull red from 0.03 W, orange near 0.3 W, yellow-white at its rated 0.75 W
- 4 mm sockets: red +, black −; plugs stack to make a junction
- Tray: drag a part out; drag it back to remove it
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More physics sims
- Adding vectors by scale drawing simSet two forces or two velocities, pick a scale, draw them head to tail or as a parallelogram, then measure the resultant with a ruler and a protractor and compare it with the calculated value.
- Atom and nuclide builder simDrag protons, neutrons and electrons into an atom; read Z, A, the element, the nuclide notation and the charge, see whether the nucleus is stable or radioactive, and compare isotopes side by side.
- Centre of gravity of a plane lamina simHang a card from a pin at three holes, mark the plumb line each time, find the centre of gravity where the lines cross, and check it by balancing on a pencil point.
- Charging by rubbing: only electrons move simRub a polythene, acetate or glass rod with wool or silk, watch electrons move from one to the other, then bring the rod near a hanging charged rod or scraps of paper: like charges repel, unlike attract, and a charged rod pulls a neutral one.
- Circular motion: the whirling bung simWhirl a rubber bung on a string: set its speed, radius and mass and read the pull on a newton-meter, let go and watch it leave along the tangent, then hang slotted masses on the string, whirl until the paper clip holds steady, time ten turns and plot F against v².
- Convection in water and air simDrag a Bunsen burner or an immersion heater and a potassium permanganate crystal around a beaker of water and watch the purple trace the convection loop (or stay put when the water is heated at the top), then pull smoke through a candle-heated chimney box and drag the sun to turn a sea breeze into a land breeze.