Discovery and Development
– Ancient people learned about magnetism from lodestones, naturally magnetized pieces of iron ore.
– The word ‘magnet’ was adopted from Latin and Greek, referring to lodestones found in Anatolia.
– In 11th century China, it was discovered that quenching red hot iron in the Earth’s magnetic field would leave the iron permanently magnetized.
– Magnetic compasses were used in navigation by the 12th to 13th centuries in various regions.
– The horseshoe magnet was invented in 1743 to overcome the demagnetization of straight iron magnets.

Physics – Magnetic Field
– The magnetic flux density, or magnetic B field, is a vector field that has both direction and magnitude.
– The direction of the magnetic field is along the orientation of a compass needle.
– The strength of the magnetic field is given in teslas.

Physics – Magnetic Moment
– A magnet’s magnetic moment characterizes its overall magnetic properties.
– For a bar magnet, the magnetic moment points from the south pole to the north pole.
– The magnitude of the magnetic moment relates to the strength and distance between the poles.
– The strength of the magnetic field produced by a magnet is proportional to the magnitude of its magnetic moment.
– When a magnet is put into an external magnetic field, it experiences a torque and may be subject to a driving force.

Physics – Magnetization
– The magnetization of a magnetized material is the local value of its magnetic moment per unit volume.
– It is a vector field that can have different directions and strengths in different areas of the magnet.
– A good bar magnet may have a magnetic moment of magnitude 0.1A·m and an average magnetization magnitude of 100,000A/m.
– Iron magnets can have a magnetization of around a million amperes per meter.

Types and Uses of Magnets
– A magnet is a material or object that produces a magnetic field and can attract or repel other magnets.
– Permanent magnets are made from materials that are magnetized and create their own persistent magnetic field.
– Ferromagnetic materials, such as iron, nickel, and cobalt, can be magnetized and strongly attracted to magnets.
– Soft ferromagnetic materials, like annealed iron, can be magnetized but do not tend to stay magnetized.
– Hard ferromagnetic materials, such as alnico and ferrite, can be magnetized and retain their magnetism.
– Magnets are commonly used in everyday objects like refrigerator magnets.
– Electromagnets are made from coils of wire and act as magnets when an electric current passes through them.
– Electromagnets are used in various applications, such as electric motors, speakers, and MRI machines.
– Magnetic storage devices, like hard drives and magnetic tapes, use magnets to store and retrieve data.
– Magnets are used in magnetic levitation systems, where objects are suspended and moved using magnetic fields.Sources: