Magnetism
Overview
Magnetism (자기, magnetism) refers to the phenomenon of force in which a magnet attracts ferromagnetic materials such as iron, or occurs around a current-carrying wire. It is a physical interaction that forms the foundation of electromagnetism and, together with electricity, serves as a key principle of modern technology. Magnetic phenomena arise from the spin and orbital motion of electrons within matter and are one of the fundamental forces found in nature.
Main Content
Definition and Characteristics of Magnetic Field
A magnetic field (자기장, magnetic field) is a vector field formed in space by a magnet or electric current, representing the strength and direction of magnetic force. Its unit is the tesla (T) or gauss (G), and the direction of the magnetic field is from the north pole to the south pole. According to Gauss's law for magnetism, one of Maxwell's equations, magnetic field lines always form closed curves, and magnetic monopoles do not exist.
Types of Magnetic Materials
Materials are broadly classified into three types based on their response to an external magnetic field. Ferromagnets (강자성체, ferromagnet) are materials such as iron, nickel, and cobalt that exhibit magnetism even without an external magnetic field and have a magnetic domain structure. Paramagnets (상자성체, paramagnet) are materials like aluminum and platinum that exhibit weak magnetism only in the presence of an external magnetic field. Diamagnets (반자성체, diamagnet) are materials such as copper and bismuth that exhibit weak magnetism in the opposite direction to the external magnetic field.
Electromagnetic Induction
Electromagnetic induction (전자기 유도, electromagnetic induction), discovered by Michael Faraday in 1831, is the phenomenon in which a changing magnetic field generates an electric field. This is a core principle of modern power systems such as generators, transformers, and induction motors, and is mathematically described by Faraday's law. The induced electromotive force is proportional to the time rate of change of the magnetic field, and according to Lenz's law, the induced current flows in a direction that opposes the change in the magnetic field.
Magnetic Resonance and Applications
Magnetic resonance (자기 공명, magnetic resonance) is a phenomenon in which electromagnetic waves of a specific frequency alter the spin state of atomic nuclei in a magnetic field. This is the basic principle of MRI (magnetic resonance imaging), which images the distribution of hydrogen nuclei in the human body for medical diagnosis. Additionally, nuclear magnetic resonance spectroscopy (NMR) is used for molecular structure analysis.
Earth's Magnetic Field
The Earth has a geomagnetic field (지구 자기장, geomagnetic field) generated by convective motion in its outer core. This magnetic field acts as a shield protecting the Earth from the solar wind and plays a crucial role in compass direction indication and migratory bird navigation. The Earth's magnetic field reverses polarity approximately every 250,000 years, and the north magnetic pole is currently moving from northern Canada toward Siberia.
Recent Trends
As of 2024-2025, the following major developments are occurring in the field of magnetism. First, magnetic levitation train technology using high-temperature superconductors has entered the practical stage, with tests of superconducting maglev trains exceeding 600 km/h underway in Japan and China. Second, in the field of spintronics (스핀트로닉스, spintronics), next-generation memory devices (MRAM) utilizing electron spin have been commercialized, with products consuming over 90% less power than conventional semiconductor memory. Third, in quantum computing, magnetic field shielding technology to enhance the stability of superconducting qubits has advanced, successfully reducing error rates to the 10^-5 level. Fourth, NASA and ESA are developing high-sensitivity magnetometers to be mounted on Mars probes in 2025, expected to help elucidate the internal structure of Mars and the cause of its past magnetic field disappearance. Additionally, advances in magnetic field simulation technology using artificial intelligence have been reported to reduce electromagnetic device design time by 70%.
Related Topics
- [[Electromagnetism]]
- [[Superconductor]]
- [[MRI]]
- [[Spintronics]]
- [[Geophysics]]
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