Electromagnets
Describe the magnetic effect of an electric current (a current-carrying wire produces a magnetic field), and investigate how the strength of an electromagnet depends on current, number of coil turns, and core material
What a learner can do afterwards
- Describes that a current-carrying wire produces a circular magnetic field
- Lists three factors that affect electromagnet strength: current size, number of coil turns, and core material
- Explains why an electromagnet can be switched on and off, unlike a permanent magnet
The lesson
You already know that current is the flow of charge through a wire, and that a magnetic field can pull on certain metals. Put those together and you get an electromagnet: whenever current flows through a wire, the wire creates its own magnetic field, circling around it like invisible rings.
Zara wraps a wire around an iron nail 20 times and connects both ends to a battery. Current flows, the coil's magnetic field lines up inside the iron, and the nail becomes strong enough to pick up 5 paperclips. When she disconnects one wire, the current stops, the field disappears, and the paperclips fall off.
The core matters as much as the coil. An iron nail becomes strongly magnetic inside a coil, but a plastic or wooden rod barely helps at all, because only certain metals respond strongly to a magnetic field.
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.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.