Permanent magnets are objects that have a strong and lasting magnetic field, even when they are not exposed to an external magnetic field. This is due to the fact that the magnetic domains within the object are aligned in the same direction, creating a strong overall magnetic field. Permanent magnets are often made from materials such as iron, nickel, and cobalt, which are known as ferromagnetic materials.
Temporary magnets are objects that only exhibit magnetic properties when they are exposed to an external magnetic field. This is due to the fact that the magnetic domains within the object are not aligned in the same direction, and so the overall magnetic field is weak. When the external magnetic field is removed, the magnetic domains within the object become misaligned again, and the object loses its magnetic properties. Temporary magnets are often made from materials such as aluminum, copper, and brass, which are known as paramagnetic materials.
The strength of a magnetic field is measured in teslas (T). The Earth's magnetic field is approximately 0.5 gauss (50 microteslas). Permanent magnets can have magnetic fields of up to 1.5 teslas, while electromagnets can have magnetic fields of up to 10 teslas.
Magnetic objects have a variety of applications, including:
* Magnetic compasses, which use the Earth's magnetic field to determine direction.
* Electric motors, which use magnetic fields to convert electrical energy into mechanical energy.
* Magnetic resonance imaging (MRI), which uses magnetic fields to produce images of the inside of the body.
* Magnetic levitation (maglev), which uses magnetic fields to levitate objects, such as trains.
