How can you demagnetize metal and what is the concept of a demagnetizer?

Answer 1

To demagnetize (degauss) a metal, you can heat it above its Curie temperature and cool it and the magnetic properties will not return. But this is probably not what we're looking for. Degaussing a metal is usually done by "sweeping" it with an alternating magnetic field. That what a degaussing coil does. It's often powered by the 60 cycle per second AC field of the power grid (50 Hertz in lots of places other than the US). Take a coil, include enough windings in it to provide sufficient inductive feedback (so you won't short the line) and you've got a degaussing coil. You may or may not want to include a core. Bulk tape erasers (they're still around) have a core, and TV's with CRT's can be degaussed with a coil that does not have a core built in (it's an air core inductor). The coil (with or without core) has a switch and a power plug. Plug it in, turn it on, and either move the magnet you want to demagnetize around in the field or move the field around the magnet. Slowly move the field away from the (now demagnetized) magnet to decouple it, and turn it off. You've "swept" the magnetic field from the magnet. Tool degaussers work the same way. The duty cycle of degaussers varies, and they come in different sizes and shapes, depending on the application. The heart of the degausser is the AC coil, with or without core. Go to a site like eBay and use "demagnetizer" or "degausser" in your search argument and look at the pictures. Some portable units have a battery to power them up, but the battery will be tied to a circuit that creates AC or pulsating DC (with its "cycling" magnetic field) to provide the degaussing action.