Magnetic influence: The generation of magnetism by external magnetic fields

Magnetic influence, also known as magnetic induction, describes the process in which a material is magnetised by an external magnetic field without direct contact with a magnet. This process is a central principle in magnetism and is frequently used in physics and technology, for example in electromagnets and transformers.

How does magnetic influence work?

In magnetic influence, the magnetic domains within a material are aligned when the material is exposed to an external magnetic field. This process occurs in several steps:

• Original state: The magnetic domains in the material are randomly aligned, making the material non-magnetised overall.
• Exposure to a magnetic field: The external field causes the domains to align parallel to the field, creating a magnetic effect.
• Loss of magnetisation: As soon as the external field is removed, the material either returns to its original state (in the case of soft magnetic materials) or retains a residual magnetisation (in the case of hard magnetic materials).

Properties of magnetic influence

• Contactless process: Magnetic influence does not require direct contact between the magnet and the influenced material.
• Material dependence: The strength of the influence depends on the properties of the material, such as permeability and saturation magnetisation.
• Reversibility: In soft magnetic materials, the magnetic influence is completely reversible, while a residual magnetisation remains in hard magnetic materials.

Examples of magnetic influence

• Nail and magnet: An iron nail becomes magnetised when brought close to a magnet and can temporarily attract other iron objects.
• Induction in transformers: In transformers, magnetic influence is used to transfer electrical energy between coils.
• Electromagnets: Magnetic influence creates a strong magnetic field in soft magnetic cores surrounded by a current-carrying coil.

Applications of magnetic influence

Magnetic influence has numerous practical applications in science and technology:

• Electric motors: The magnetisation of cores by electric current is based on the principle of magnetic influence.
• Magnetic shielding: Materials such as soft iron are magnetically influenced to deflect external magnetic fields.
• Sensor technology: Magnetic influence is used in Hall sensors and other measuring devices to detect magnetic fields.
• Medical technology: Magnetic induction is used in MRI (magnetic resonance imaging) devices to generate signals from tissue.

Interesting facts about magnetic influence

Did you know that magnetic influence is one of the oldest discovered properties of magnetism? Even in ancient times, people observed that iron in the vicinity of natural magnets such as magnetite also took on magnetic properties. Today, this phenomenon is the basis for many key technologies, such as the generation and transmission of energy.