What is the difference between a permanent magnet and an electromagnet?
In an electromagnet the magnetic field is created through electric current in a wire-wound coil and strengthened by a soft-iron core. As soon as you turn off the power, the soft-iron core loses its magnetisation.
A permanent magnet is made of ferromagnetic material, which is magnetised by a strong external magnetic field. The magnetically hard material that is used keeps part of its magnetisation after the external magnetic field is turned off.
Note: We only carry permanent magnets in our shop, no electromagnets.
Table of Contents
Magnetic fields (B fields) in generalAll magnetic fields (B fields) are created by electric charges or currents. Even a single charged electron produces a B field.
A wire with an electric current (charged electrons) produces a magnetic field in its surroundings. The strength of the magnetic field depends on the intensity of the current and the shape of the wire. Each wire with a current flow is practically an electromagnet.
The orange arrow indicates the technical direction of the current. Historically, it is opposite of the direction of the electrons.
Soft-iron coreWhen it comes to electromagnets, usually a soft-iron core is placed in the coil, which considerably strengthens its magnetic field, because the magnetic field of the coil magnetises the soft-iron core and, thereby, creates an additional magnet. The soft-iron core loses its magnetisation after the current is turned off. This is desirable in order to be able to turn the magnet on and off.
Magnetically soft and hard ironThe term "magnetically soft" refers to the fact that mechanically soft iron loses its magnetisation, while carbon-enriched, mechanically hard iron (steel) keeps part of its magnetisation. This is called remanence. "Remanere" comes from the Latin "remain". Material with a high remanence is called "magnetically hard".
Live solenoids are used to magnetise permanent magnets such as our super magnets, which are made of magnetically hard materials.