Some metal detectors can discriminate between various metals, allowing users to decide if a particular discovery would be worth digging up. A significant percentage of hits are indeed pieces of metallic trash or discarded building materials. Part of the appeal of this hobby, however, is discovering a lost class ring or a piece connected with local history. Some professional treasure hunters use very discriminating detectors set only for valuable metals, but hobbyists tend to explore even the less lucrative hits.
Metal detectors are electronic devices that are used to find traces of metal usually from the ground, a person, or cargo. This metal could be anything from discarded pieces of aluminum to buried treasures. These devices can penetrate sand, soil, wood and other non-metallic substances.
Most metal detectors, hand held, and the walk-through ones at the airport utilize a field-disturbance detector. That is a fancy name for a simple concept. When a conductor passes through a magnetic field, a portion of that magnetic field is disturbed, distorted and reduced. That reduction in the magnetic field is related to a small amount of current that is induced or created in the conductor.
You can do the same thing by jumping rope with a piece of wire instead of the rope. As the wire cuts through the earth's magnetic field, a small amount of electricity is generated at the end of the wires.
Electromagnetic induction is the creation of an electric field by a fluctuating magnetic field. The electric field may be produced, according to Faraday's law of induction in two ways: by the motion of a conductor cutting across the lines of magnetic flux of a magnetic field or by a change in the magnetic flux passing through a coil immersed in a non constant magnetic field.
