Magnetism

Understanding magnetic fields, magnetic forces, and electromagnetic induction

Topics

How do electric motors work?

Electric motors work by using electromagnetic forces—electric current in coils creates magnetic fields that interact with permanent magnets or other magnetic fields, creating forces that cause rotation. The motor converts electrical energy into mechanical work through the interaction of magnetic fields.

How do generators work?

Generators work by electromagnetic induction—rotating coils of wire in magnetic fields create changing magnetic flux, which induces electric current according to Faraday's law. Mechanical energy (from turbines, engines, etc.) rotates the coils, converting mechanical energy into electrical energy.

How do magnets work?

Magnets work through magnetic fields created by aligned magnetic domains in materials. Permanent magnets have domains aligned by their atomic structure, while electromagnets create fields through electric current flowing through coils.

How does a compass work?

A compass works because its magnetic needle aligns with Earth's magnetic field. The needle is a small magnet that points toward magnetic north, allowing navigation by showing direction relative to Earth's magnetic poles.

What is a magnetic field?

A magnetic field is a region around a magnet or moving electric charge where magnetic forces act on other magnets or moving charges. It's invisible but can be detected by its effects on magnetic materials and compasses.

What is a solenoid?

A solenoid is a coil of wire wound in a helical shape that creates a uniform magnetic field when electric current flows through it. Solenoids are used as electromagnets, with applications ranging from door locks to scientific instruments, creating strong magnetic fields in a controlled manner.

What is electromagnetic induction?

Electromagnetic induction is the process of generating electric current by changing magnetic fields. When a magnetic field changes near a conductor, it creates an electric field that drives current, as described by Faraday's law.

What is magnetic flux?

Magnetic flux is a measure of the total magnetic field passing through a given area. It's calculated as flux = magnetic field × area × cosine of the angle between field and area normal. Magnetic flux represents how much magnetic field 'flows' through a surface and is measured in webers.

Why do magnets attract metal?

Magnets attract certain metals (like iron, nickel, and cobalt) because these ferromagnetic materials have unpaired electrons that align with the magnet's magnetic field, creating attraction through magnetic forces.

Why do magnets lose their magnetism?

Magnets lose their magnetism when magnetic domains become misaligned due to heat, mechanical shock, or exposure to opposing magnetic fields. High temperatures can randomize domain alignment, while physical impacts or strong opposing fields can disrupt the ordered magnetic structure that creates magnetism.