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Magnet is defined as a material that can produce its own magnetic field. There are three types of magnet: permanent magnet, temporary magnet, and electromagnet. Magnets are used in electric bells and generators.
- Uses of Magnets
The small coil of wire and a magnet inside a speaker...
- Magnetic Field
The research on the magnetic field began in 1269 when French...
- Electricity And Magnetism
Hope you understand magnetism and electricity definition,...
- Uses of Magnets
Electromagnetic induction can create a voltage by movement of a conductor in a magnetic field. This voltage can make current flow, and the effect is used in electricity generation and...
Nov 5, 2019 · Magnetism is defined as an attractive and repulsive phenomenon produced by a moving electric charge. The affected region around a moving charge consists of both an electric field and a magnetic field. The most familiar example of magnetism is a bar magnet, which is attracted to a magnetic field and can attract or repel other magnets.
- Anne Marie Helmenstine, Ph.D.
- Overview
- Fundamentals
magnetism, phenomenon associated with magnetic fields, which arise from the motion of electric charges. This motion can take many forms. It can be an electric current in a conductor or charged particles moving through space, or it can be the motion of an electron in an atomic orbital. Magnetism is also associated with elementary particles, such as ...
Basic to magnetism are magnetic fields and their effects on matter, as, for instance, the deflection of moving charges and torques on other magnetic objects. Evidence for the presence of a magnetic field is the magnetic force on charges moving in that field; the force is at right angles to both the field and the velocity of the charge. This force deflects the particles without changing their speed. The deflection can be observed in the torque on a compass needle that acts to align the needle with the magnetic field of Earth. The needle is a thin piece of iron that has been magnetized—i.e., a small bar magnet. One end of the magnet is called a north pole and the other end a south pole. The force between a north and a south pole is attractive, whereas the force between like poles is repulsive. The magnetic field is sometimes referred to as magnetic induction or magnetic flux density; it is always symbolized by B. Magnetic fields are measured in units of tesla (T). (Another unit of measure commonly used for B is the gauss, though it is no longer considered a standard unit. One gauss equals 10−4 tesla.)
A fundamental property of a magnetic field is that its flux through any closed surface vanishes. (A closed surface is one that completely surrounds a volume.) This is expressed mathematically by div B = 0 and can be understood physically in terms of the field lines representing B. These lines always close on themselves, so that if they enter a certain volume at some point, they must also leave that volume. In this respect, a magnetic field is quite different from an electric field. Electric field lines can begin and end on a charge, but no equivalent magnetic charge has been found in spite of many searches for so-called magnetic monopoles.
The most common source of magnetic fields is the electric current loop. It may be an electric current in a circular conductor or the motion of an orbiting electron in an atom. Associated with both these types of current loops is a magnetic dipole moment, the value of which is iA, the product of the current i and the area of the loop A. In addition, electrons, protons, and neutrons in atoms have a magnetic dipole moment associated with their intrinsic spin; such magnetic dipole moments represent another important source of magnetic fields. A particle with a magnetic dipole moment is often referred to as a magnetic dipole. (A magnetic dipole may be thought of as a tiny bar magnet. It has the same magnetic field as such a magnet and behaves the same way in external magnetic fields.) When placed in an external magnetic field, a magnetic dipole can be subjected to a torque that tends to align it with the field; if the external field is not uniform, the dipole also can be subjected to a force.
All matter exhibits magnetic properties to some degree. When placed in an inhomogeneous field, matter is either attracted or repelled in the direction of the gradient of the field. This property is described by the magnetic susceptibility of the matter and depends on the degree of magnetization of the matter in the field. Magnetization depends on the size of the dipole moments of the atoms in a substance and the degree to which the dipole moments are aligned with respect to each other. Certain materials, such as iron, exhibit very strong magnetic properties because of the alignment of the magnetic moments of their atoms within certain small regions called domains. Under normal conditions, the various domains have fields that cancel, but they can be aligned with each other to produce extremely large magnetic fields. Various alloys, like NdFeB (an alloy of neodymium, iron, and boron), keep their domains aligned and are used to make permanent magnets. The strong magnetic field produced by a typical three-millimetre-thick magnet of this material is comparable to an electromagnet made of a copper loop carrying a current of several thousand amperes. In comparison, the current in a typical light bulb is 0.5 ampere. Since aligning the domains of a material produces a magnet, disorganizing the orderly alignment destroys the magnetic properties of the material. Thermal agitation that results from heating a magnet to a high temperature destroys its magnetic properties.
Magnetic fields vary widely in strength. Some representative values are given in the Table.
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Magnetism and electromagnetism. Magnetic fields - AQA. Magnetism is due to the magnetic fields around magnets. The fields can be investigated by looking at the effects of the forces...
Jul 22, 2022 · Magnetic energy is the energy associated with a magnetic field. Since electric currents generate a magnetic field, magnetic energy is due to electric charges in motion. Magnetic fields are generated by permanent magnets, electromagnets, and changing electric fields.
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Similar to how an electric charge experiences a force in an electric field, a magnet or an electric current experiences a force in a magnetic field. The unit of a magnetic field is Tesla (T). Magnetic field patterns. Magnetic fields can be graphically represented using magnetic field lines.
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