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Nail Electromagnet

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Recipe #33 — nail electromagnet

Inductors begin with a very physical idea: current through a coil creates a magnetic field. Wrap insulated wire around an iron nail and the effect can pick up steel objects.

NAIL ELECTROMAGNET 3–6 V BATTERYSW1 IRON NAIL / CORE INSULATED WIRE COIL magnetic field strengthens when current flows More turns and more current generally increase magnetizing force — until heating or core saturation becomes important.
Close SW1: current flows through the coil and produces a magnetic field. The iron nail provides a low-reluctance path that greatly strengthens and concentrates the field.

Ampere-turns

A useful beginner idea is turns × current. More coil turns or more current can produce a stronger magnetizing force. That does not mean either can be increased without limit.

Two limits appear quickly

Heating: wire resistance turns electrical power into heat. Core saturation: beyond some magnetizing force, the iron cannot increase its magnetic flux in proportion to current anymore. Pushing more current then mostly creates more heat.

Practical caution: use low voltage and limit current. A coil connected directly to a battery can become hot enough to damage insulation or the battery.

Try these yourself

What creates the magnetic field in the nail electromagnet?
Electric current through the winding produces the magnetic field.
What is the purpose of the iron nail?
The ferromagnetic core provides an easier path for magnetic flux and strengthens the electromagnet.
Why can increasing current eventually be a bad idea?
Copper heating increases with current, while an iron core eventually approaches magnetic saturation.
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