Switchable Electromagnet
Coil insulated wire around an iron bolt and a battery turns it into a magnet you can switch on, off, and strengthen at will.
Start building ↓The build
Wind the coil
Wrap the wire in neat, same-direction turns around the bolt.
Strip the ends
Bare the last cm of each wire end for metal contact.
Connect the battery
Touch one end to each terminal to complete the circuit.
Pick up clips
Bring the bolt near paper clips — they jump up; disconnect and they drop.
Moving charge creates a magnetic field; coiling the wire stacks each loop's field while the iron core concentrates the field lines into a strong magnet.
A closer look
More turns and more current both raise the field strength. The same principle drives doorbells, relays and scrapyard cranes.
Variables to test
- 1 Double the turns and re-count the clips lifted.
- 2 Swap to an aluminium bolt — why does the pull nearly vanish?
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