Electromagnets at work: relay, bell, circuit breaker sim
Close a relay's coil switch and watch a 58 mA coil current pull the armature down and switch on a separate 12 V lamp circuit carrying 2.91 A; step an electric bell through its make-and-break cycle one stage at a time; switch on lamps or join a fault until a model circuit breaker trips, and find that it will not reset until the fault is removed.
Electromagnetism: uses of electromagnets · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Bench models with chosen values, solved by one circuit solver. Relay: coil circuit 1.5 V or 3 V cells through a 50 Ω coil (29.2 mA or 58.0 mA; pull-in at 40 mA); lamp circuit 12 V through a 12 V 36 W lamp (2.91 A). Bell: two cells through two 1.5 Ω coils (0.82 A while the contact is closed, 0 A while it is open). Breaker: 12 V through up to three 12 V 24 W lamps in parallel (the ammeter reads 2.0, 3.8, 5.7 A; a little under 2.0, 4.0 and 6.0 A from the ratings, because the supply and the leads take a little of the 12 V) or a 0.05 Ω fault (about 70 A); trips above 5.0 A. Nothing here runs on mains.
- The soft iron that moves: the relay's armature, the bell's armature, the breaker's catch
- Copper coils on soft-iron cores (the electromagnets); thin blue lines are the wiring fixed to the boards
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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