Build yours at home · Build 006
Turn a bolt into a magnet
What we're doing
Wrap wire round a bolt and send electricity through it. The bolt becomes a magnet, but only while the electricity flows.
About 15 minutes.
Goes with these lessons
Get these parts
- A big iron bolt or nail (household)
- A small spool of thin insulated wire, about 16 feet (5 meters) (hardware or electronics shop)
- 2×AA battery holder with a switch (electronics shop or online)
- Small paper clips (household)
Fill each holder with the matching number of AA batteries (household).
Keep it safe
Battery power only, never household power. Use AA packs matched to the parts, not a 9V battery. A grown-up connects and disconnects the pack. Stop immediately if any part warms. Never join the pack's two metal ends: the wires can get hot. Coin cells stay with grown-ups, locked away. CPSC warns a swallowed button or coin cell can burn through a child's throat in about two hours; suspected swallowing needs emergency medical care immediately.
Switch on for a few seconds at a time. The wire and battery get warm fast; switch off if they do.
Steps
- 1
Leave a hand's length of wire free, then wrap the wire round the bolt 20 times, neatly, all in one direction.
- 2
A grown-up strips a thumb's width of plastic off both wire ends and twists one to each battery wire. Keep the switch off.
- 3
Switch on and touch the bolt to the clips. Count how many it picks up. Switch off: the clips fall.
- 4
Wrap 20 more turns and count again. More turns, more clips.
- 5
Switch off and put the clips away.
Talk while you build
- What happens to the clips when we unplug the battery?
- How is this bolt different from a fridge magnet?
Spot it at home
- Scrapyard cranes that lift a car, then drop it. Ding-dong doorbells, where an electromagnet throws a rod at the chime. Speakers and headphones.
Why would a crane want a magnet it can switch off?
More for grown-ups · printed parts
Optional equipment
Prints that make the build easier. None are required. Every build works with tape and clips.
Printables
The same frame from Build 001, now with the bolt in as the core.
Not printed yet
Instructables
An electromagnet that pulls a lever and clicks. The relay in Build 008 works the same way.
Not printed yet
Grown-up references
Electronics for Kids · Øyvind Nydal Dahl Has an electromagnet project using a coil and an iron core.