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When you walk through a metal detector carrying a metal object in your pocket, it raises an alarm. This phenomenon works on:
- Electromagnetic induction
- Resonance in ac circuits
- Mutual induction in ac circuits
- Interference of electromagnetic waves
Correct answer: Electromagnetic induction
Solution
A metal detector's oscillating coil sets up a changing magnetic field that induces eddy currents in a nearby metal object; these alter the coil's signal and trigger the alarm. This is electromagnetic induction.
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