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At an airport, a perosn is made to walk...

At an airport, a perosn is made to walk through the door wy of a metal detector, for security reasons. If `she//he` is carrying anything made of metal, the metal detector emits a sound. On what principle does this detector work ?

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The metal detector works on the principle of resonance in a.c. circuits.
When we walk through a metal detectot, we are infact, walking through a coil of many turns connected to a capacitor turned suitably. If we carry some metal on our body, impedance of the circuit changes, bringing about significant changes in the current. This change in current is detected and the eletronic circuitry causes an alarm.
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