Metal detector is meant to detect the presence of which of the following in the search object ?

Metal detectors operate on the principle of electromagnetic induction. The device contains a coil that produces an alternating magnetic field. When this field passes over a conductive object, it induces eddy currents within that object. These currents generate their own magnetic field, which the detector's receiver coil senses, triggering an alert.

• Ferrous metals (such as iron and steel) are both magnetic and conductive, making them easily detectable.
• Non-ferrous metals (such as copper, aluminum, gold, and silver) are not magnetic but are excellent electrical conductors; therefore, they also produce eddy currents and are detected.
• Plastic is an insulator (non-conductive) and non-magnetic. It does not interact with the electromagnetic field to produce eddy currents, so it cannot be detected by a standard metal detector.