Grade 12 · ⚛️ Physics · Electromagnetism
Build an electromagnet from a nail
Wrap wire around an iron nail, connect a battery, and pick up pins. Then change the number of turns and measure the difference.
Why this matters
Electromagnets are inside every electric motor, loudspeaker and power transformer — from the grain mills in rural towns to the turbines at Gibe III. Scrapyard cranes use giant electromagnets to lift cars. Your nail works on exactly the same principle.
Watch the demo
Video coming soon
We're recording a demo for this experiment. Until then, follow the step-by-step guide below.
The science
Current makes a magnetic field
Any electric current produces a magnetic field around the wire. Coiling the wire into a solenoid concentrates the field inside the coil.
Making it stronger
An iron core greatly strengthens the field. The field inside a solenoid is B = μ·n·I, so more turns per length (n) or more current (I) make a stronger magnet.
You'll need
- A large iron nail (about 8–10 cm)
- About 1 m of thin insulated copper wire↳ Strip it from an old phone charger cable
- A 1.5 V D-cell or AA battery and some tape
- Paper clips or pins
- Sandpaper or a knife to strip the wire ends (adult help)
Safety first
- Use only small batteries — never a car battery or wall socket.
- The wire and battery can get hot. Connect only for a few seconds at a time.
- Ask an adult to strip the wire ends with a knife.
Step by step
0/5 doneWhat you should see
With current flowing, the nail picks up paper clips; when you disconnect the battery, most of them drop. More turns pick up more clips.
Why it happens
The current in the coil creates a magnetic field that magnetises the iron core. More turns means a stronger field, as B = μ·n·I predicts. When the current stops, the field disappears — which is why electromagnets can be switched on and off, unlike permanent magnets.
Didn't work? Try this
Nothing is attracted.
Check the bare wire ends make good contact with the battery terminals, and that the insulation was fully removed.
Clips stay stuck after I disconnect.
The nail has become slightly permanently magnetised (common with steel nails). That's normal — tap it on a table to reduce it.
The battery gets hot quickly.
You've made a short circuit. Disconnect between tests and only connect for a few seconds.
Still stuck? Ask the lab assistant
Check your understanding
1. What happens to the electromagnet's strength if you double the number of turns?
2. Why does the electromagnet drop the clips when the battery is disconnected?
Your lab notebook
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