Question

At the airport, a person is made for walking through a doorway of a metal detector for security reasons. If he is carrying anything made of metal, the metal detector emits a sound. On what principle does the metal detector work?

Answer 1

Hint:A metal detector is an electronic device used to detect the metal presence nearby. These detectors are useful to find the metal made object hidden by someone or the presence found at some particular range. Mostly these are used in airports and for prison for security purposes. Different types of metal detectors are beat-frequency oscillation; very low frequency, pulse induction.

Complete step by step answer:
It works on the principle of electromagnetic induction. The simplest form of a metal detector consists of an oscillator producing an A.C that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, which produces a magnetic field of its own. If another coil is used to measure the magnetic field, the magnetic field change due to the metallic object can be detected.

Therefore the principle on which metal detector is based is electromagnetic induction.

Note:The most difficult metal to detect is stainless steel. The instrument cannot detect because it has poor electrical conductivity. Stainless steel has low magnetic permeability, which means that it does not produce a strong signal enough to be identified. The metal detecting range is 5 kHz to 15 kHz.

Due to research techniques in electromagnetic metals, the detector is classified into two categories:
i) Very low-frequency technology.
ii) Pulse induction technology.
Pulse induction technology works on electromagnetic induction, and very low frequency works on mutual induction. Mutual induction is also based on electromagnetic induction. That is why we consider the principle of metal detectors is electromagnetic induction.