What is the difference between a permanent and an induced magnet?

A permanent magnet retains its magnetism, while an induced magnet becomes magnetic only in the presence of a magnetic field.

Permanent magnets, such as bar magnets or fridge magnets, have a persistent magnetic field. This means they continuously produce a magnetic field without needing any external influence. The materials used to make permanent magnets, like iron, cobalt, and nickel, have domains (tiny magnetic regions) that are aligned in the same direction, giving the magnet its lasting magnetic properties. Once these domains are aligned during the manufacturing process, they stay that way, making the magnet permanently magnetic.

Induced magnets, on the other hand, only exhibit magnetism when they are within a magnetic field. When a material like iron is placed in a magnetic field, the domains within the material temporarily align with the field, causing the material to act like a magnet. However, once the external magnetic field is removed, the domains return to their random arrangement, and the material loses its magnetism. This temporary magnetism is why induced magnets are useful in applications where a controllable magnetic effect is needed, such as in electromagnets.

Understanding the difference between these two types of magnets is crucial in various applications. Permanent magnets are used in everyday items like compasses, motors, and speakers because they provide a consistent magnetic force. Induced magnets are often used in industrial applications where the magnetic effect needs to be turned on and off, such as in cranes for lifting heavy metal objects or in electric bells.

In summary, the key difference lies in the duration and dependency of their magnetism: permanent magnets are always magnetic, while induced magnets are only magnetic when exposed to an external magnetic field.