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How does a metal detector work?

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Quick answer

A metal detector works by sending out a magnetic field that creates tiny electric currents in any nearby metal. Those currents make their own field, which the detector senses and announces with a beep — revealing metal hidden underground or in bags.

Step by step

  1. A coil generates a changing magnetic field.
  2. Metal nearby develops small swirling currents ('eddy currents').
  3. Those currents create their own magnetic field.
  4. A second coil detects that returning field and triggers a signal.
  5. Different metals respond differently, helping identify what's found.

People also ask

How does a metal detector find metal?
Its magnetic field induces tiny electric currents in nearby metal, and those currents produce a field the detector senses, setting off the beep.
Why does a metal detector beep louder near big objects?
Larger or closer metal produces stronger induced currents and a bigger return signal, so the response is stronger.
Can a metal detector tell different metals apart?
Somewhat — metals conduct differently, so the strength and timing of the signal hint at whether it's iron, gold, or aluminum.

Part of the guide: Everyday Machines →