--- title: "Electromagnets" description: "Describe the magnetic field made by a current and investigate how electromagnet strength depends on current, coil turns and core material, within safe limits." canonical: https://lightmysky.com/learn/science/electromagnets-mt_2qkn8Lhc8e source: https://lightmysky.com/learn/science/electromagnets-mt_2qkn8Lhc8e.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Electromagnets Describe the magnetic field made by a current and investigate how electromagnet strength depends on current, coil turns and core material, within safe limits. Subject: Science · Area: Forces & Motion · Ages 12 to 13 Page: https://lightmysky.com/learn/science/electromagnets-mt_2qkn8Lhc8e ## Ready when they can - Describes that a current-carrying wire produces a circular magnetic field - Lists three factors that can affect electromagnet strength: current size, number of coil turns and core material, while recognising that the variables must be compared safely. - Explains why an electromagnet can be switched on and off, unlike a permanent magnet ## Lesson: Electromagnets: magnets you can switch on Current is charge flowing through a wire. A magnetic field is the invisible area around a magnet where it can pull on certain metals. A compass needle is a small magnet that lines up with the field at its position. Current in a straight wire makes a field that circles the wire like invisible rings. This field can turn a nearby compass needle. A visible turn depends on the field's strength and direction at the compass. Scientists used this effect to detect the field. Coiling a wire makes its loop fields add inside the coil. More turns per coil length, more current or an iron core can strengthen the field. For a fair test, change one factor; keep current, core size and coil dimensions fixed unless they are the tested factor. The same battery may give a different current after rewinding. Stay within safe limits: current can heat wire. When a question gives a repeating clip-count pattern, find the increase per step and add it for each new step. *(drawing: Current, nail and coil dimensions stay the same. In this test, the 30-turn coil lifts more clips than the 10-turn coil.)* **Example.** Zara winds wire 20 times around a soft iron nail and connects it to a battery. The coil's field lines up many domains in the iron, and the nail lifts 5 paperclips. Disconnecting a wire stops current and the coil's field. The clips fall, though the core may keep a little magnetism. Doubling a clip count means multiplying it by 2. A doubled clip count does not prove the field strength doubled. The core matters as well as the coil. Iron contains tiny regions called domains, and each one acts like a mini magnet. With no field they point many ways. The coil's field lines many of them up, and they add their own magnetism. In soft iron most of them fall out of line when the current stops, so the boost fades. Wood and plastic have no domains, so they give no boost. *(drawing: An electric bell in order: pressing the button lets current flow so the magnet pulls the hammer. Let go, the current stops, and the hammer springs back.)* Closing a switch lets current flow; opening it stops coil current and field. A crane can then release a car. Soft iron may retain magnetism. A permanent fridge magnet needs no circuit. If pickup fails, check for a loose wire or weak battery: current may be absent or too small. For clip counts, subtract the smaller from the larger. Press a bell button to power the electromagnet that pulls the hammer. Let go: current stops; the hammer springs back and stops striking. The gong may sound briefly. **Recap.** A current-carrying wire always makes a magnetic field, and you can make an electromagnet stronger with more current, more coil turns, or an iron core, then switch it off just by breaking the circuit. *Adapted from OpenStax College Physics (CC-BY 4.0), openstax.org* · [license](https://creativecommons.org/licenses/by/4.0/) ## Practice 30 questions on this page, each with its working shown. ## Needs first - [Current, voltage, and what they measure](https://lightmysky.com/learn/science/current-voltage-and-what-they-measure-mt_2bnXrfS4Iq) - [Magnetic Fields](https://lightmysky.com/learn/science/magnetic-fields-mt_56aspHjU19) ## Opens up - [Motors & the Motor Effect](https://lightmysky.com/learn/science/motors-and-the-motor-effect-mt__7BVYUN180) - [Electromagnetic induction and generators](https://lightmysky.com/learn/science/electromagnetic-induction-and-generators-mt_e0jgUKANT-)