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Permanent Magnets and Electromagnets - SS1 Physics Lesson Note

Permanent magnets and electromagnets are two types of magnets that exhibit magnetic properties but differ in their generation and persistence of magnetism. Let's explore each type:

1. Permanent Magnets:

Permanent magnets are materials that retain their magnetism even when not in the presence of an external magnetic field. They are made from ferromagnetic materials such as iron, nickel, and cobalt, or their alloys. Key characteristics of permanent magnets include:

-       Magnetization: Permanent magnets are magnetised during the manufacturing process by aligning the magnetic domains within the material. This alignment creates a net magnetic field throughout the material, resulting in a north and south pole.

-       Persistence of Magnetism: Once magnetised, a permanent magnet will retain its magnetic properties indefinitely unless demagnetized by an external magnetic field, excessive heat, or physical shock.

-       Strength: Permanent magnets vary in strength depending on the material and the manufacturing process. They can range from relatively weak magnets used in refrigerator magnets to strong magnets used in industrial applications.

-       Applications: Permanent magnets find applications in various fields, including electric motors, generators, speakers, magnetic separators, MRI machines, and magnetic storage devices.

2. Electromagnets:

An electromagnet is a type of magnet that produces a magnetic field when an electric current flows through a coil of wire. Unlike permanent magnets, electromagnets rely on the presence of an electric current to generate a magnetic field. Key characteristics of electromagnets include:

-       Coil of Wire: An electromagnet consists of a coil of wire wound around a core, which is typically made of ferromagnetic materials such as iron. When an electric current flows through the wire, a magnetic field is created.

-       Magnetization Control: The strength of an electromagnet can be easily adjusted by varying the amount of current flowing through the coil. Increasing the current increases the magnetic field strength while decreasing the current weakens the magnetic field.

-       Temporary Magnetism: The magnetic field produced by an electromagnet only exists as long as the current is flowing. When the current is turned off, the magnetic field disappears, and the electromagnet loses its magnetism.

-       Applications: Electromagnets have a wide range of applications, including electric relays, electric motors, transformers, magnetic levitation systems, MRI machines, and particle accelerators.

In summary, permanent magnets possess inherent magnetism that persists over time, while electromagnets rely on an electric current to generate a magnetic field and only exhibit magnetism while the current is flowing. Both types of magnets play essential roles in various applications and industries.

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