magnetic field


October 28, 2021

Magnetic field, in physics, is a field that is formed by moving electric charges (electric currents) which causes a force to appear in other moving electric charges. (The quantum mechanical spin of a single particle forms a magnetic field and the spin is influenced by itself like an electric current; this is what causes the magnetic field of a "permanent" ferromagnet). A magnetic field is a vector field: that is, it corresponds to any point in vector space that can change with time. The direction of this field is equal to the direction of the compass needle placed in the field. Magnetic field is a force field that is around a magnetic object or around a current-conducting object. The magnetic field can be described by magnetic lines of force that always leave the north pole of the magnet and enter the south pole of the magnet. While in a magnet, the magnetic lines of force have a direction from the south pole of the magnet to the north pole of the magnet. The lines never intersect. The density of the magnetic lines of force indicates the strength of the magnetic field. If two magnets with different poles are brought close to each other, they will have a large magnetic field. Meanwhile, if two magnets with similar poles are brought close together, there will be no magnetic lines of force forming a magnetic field.


Maxwell's work has largely reconciled static electricity with magnetism, resulting in a set of four equations regarding the two fields. However, based on Maxwell's formula, there are still two different fields that explain different phenomena. It was Einstein who managed to show it with special relativity, that electric and magnetic fields are two aspects of the same thing (level 2 tensor), and an observer can feel magnetic forces whereas an observer in motion only feels electrostatic forces. Thus, using special relativity, the magnetic force is a manifestation of the electrostatic force of a moving electric charge, and can be predicted from knowledge of the electrostatic force and the motion of the charge (relative to an observer).

Earth's magnetic field

The earth's magnetic field is also known as the geomagnetic field. Earth is a bar magnet that has two poles, namely the North and South poles. Earth's magnetic field is generated in the fluid outer core by a dynamo process. The source of the magnetic field on Earth comes from the Earth's core, the Earth's crust, as well as in the ionosphere and magnetosphere.

Biot-Savart Law

The Biot-Savart law expresses the relationship between the electric current flowing in a path and the magnetic field that appears around the path. The Biot-Savart law describes the effect of a magnetic field on the current flowing in a conductor in a vacuum on the density of the magnetic flux. The Biot-Savart law has an equation for calculating the magnetic field as follows. ️ B ️ 0 4 ️ / ️ / s i n ️ r 2 {\displaystyle \delta \mathrm {B} {\mu _{0} \over 4\pi }{/\delta /sin\theta \over r^{2}}} B Magnetic induction (Wb/m2 or Tesla) r distance (m) /ẟ/ length of current-carrying wire element (m) K o /4π constant number 10-7 Wb A-1m-1θ Angle formed between electric current and magnetic field


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