Electromagnet strength sim
Lower a coil wound on a tube onto a dish of paper clips, switch on, lift it and count the clips it holds, then change the number of turns, the current (rheostat and ammeter) or the core (none, iron nail, steel nail) one at a time, fill a fair-test table and plot clips against turns or current with a best line, and see the steel keep some clips when switched off.
Electromagnetism: the strength of an electromagnet · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Model. The circuit is solved by the shared circuit model: 3.0 V supply (0.2 Ω inside), six 0.05 Ω leads, a switch, a 0 to 20 Ω rheostat, a 0.05 Ω ammeter reading to 0.01 A, and the coil at 0.0026 Ω per turn; the page refuses any setting above 2.0 A (the coil wire's rating, chosen). Clips lifted: a chosen model, in proportion to turns × current, 0.16 (iron), 0.1 (steel) and 0.008 (air) clips per ampere-turn, with a seeded scatter of up to ±(0.3 + 5 % of the count) per lift, rounded to whole clips. Switched off, iron keeps none and steel keeps 35 % of what it held (chosen). No saturation, no heating. Nothing runs on its own: every change is one click or drag.
- The electromagnet: drag it up and down
- Retort stand and clamp, dish of clips, power supply, switch, rheostat, ammeter
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.
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