And what is induction, anyway?
In: Engineering
Ever made an electromagnet? You can wrap wire around an iron nail and connect a battery to it. Current passing through the coil of wire induces a magnetic field in the nail. It even works in reverse- if you pass a coil of wire through a magnetic field a voltage will be induced in the wire. Electric guitar pickups consist of a coil of wire around a permanent magnet. The vibrating string distorts the magnetic field which induces the signal that the amplifier picks up. Metal detectors work by pulsing current through a coil. The brief pulse of current induces a magnetic field around the coil, which quickly collapses as the pulse ends. As the field collapses it induces its own signal in the wire which can be read by onboard processing equipment. The presence of materials which interact with a magnetic field (typically metals) slightly alters the shape of the collapsing magnetic field which tells the metal detector there’s metal in range. A traffic signal induction loop is essentially a massive metal detector embedded in the ground pointing upwards.
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