The walkthrough metal detector utilizes the law described by a Scottish physicist named James Clerk Maxwell. He discovered that magnetism and electricity are related as a rule of thumb. An example of the relationship is a coil of copper wire wrapped around the metal nail. When electric current is applied to the coil, the metal nail becomes magnetized. When an electric pulse is sent through a coil of wire, it creates a magnetic field. When the field hits a metal object, it reflects back and can be detected using another coil of wire. The size and timing of the detected pulses are used to define the size and position of the object.