IGCSE Physics 0625

4.1 Simple phenomena of magnetism

Objective: Describe the uses of permanent magnets and electromagnets

This section explores the practical applications of magnetism, focusing on both permanent magnets and electromagnets. We will examine how their properties are utilized in various technologies.

Permanent Magnets

Permanent magnets are materials that can produce a magnetic field without the need for an external power source. They are typically made from ferromagnetic materials like iron, nickel, and cobalt.

Uses of Permanent Magnets

• Holding things in place: Magnets are commonly used to hold objects together, such as refrigerator magnets, magnetic clasps on bags, and holding tools on magnetic boards.
• Electric motors: Permanent magnets are essential components in many electric motors, providing a constant magnetic field that interacts with the magnetic field produced by electric currents.
• Generators: Similar to motors, generators also rely on the interaction between magnetic fields (created by permanent magnets and moving conductors) to produce electricity.
• Magnetic separators: In industries like mining and recycling, magnets are used to separate ferrous metals (containing iron) from non-ferrous materials.
• Speakers and headphones: Permanent magnets are used in speakers and headphones to convert electrical signals into sound waves.
• Magnetic levitation (Maglev) trains: Powerful permanent magnets are used to levitate and propel Maglev trains, allowing for very high speeds.

Electromagnets

An electromagnet is a coil of wire that produces a magnetic field when an electric current flows through it. The strength of the magnetic field can be controlled by varying the amount of current and the number of turns in the coil.

Uses of Electromagnets

Use	Description
Electric motors	Electromagnets are the core component of most electric motors. The magnetic field produced by the electromagnet interacts with a permanent magnet or another electromagnet to create rotational motion.
Generators	In generators, moving a coil of wire through a magnetic field (produced by permanent magnets or other electromagnets) induces an electric current.
Lifting heavy objects: Electromagnets are used in cranes and scrap yards to lift and move heavy ferrous materials. The strength of the electromagnet can be adjusted to control the lifting force.
Magnetic resonance imaging (MRI) machines: Powerful electromagnets are used in MRI machines to create strong and uniform magnetic fields that allow for detailed imaging of the human body.
Magnetic locks: Electromagnets are used in magnetic locks, which are often found on doors and cabinets. When a current is passed through the electromagnet, it creates a strong magnetic field that holds the door or cabinet closed.
Magnetic recording devices: Electromagnets are used in hard disk drives and magnetic tape recorders to write and read data. A magnetic field aligns the magnetic particles on the recording medium to represent data.

The strength of an electromagnet can be increased by:

1. Increasing the number of turns of wire in the coil.
2. Increasing the current flowing through the wire.
3. Using a core of ferromagnetic material (like iron) inside the coil. This concentrates the magnetic field.