MAGNETIC FIELD

MAGNETIC FIELD

Flux Lines. within the area around each magnet there exists a magnetic flux. (A magnetic flux is associate example of the natural phenomenon referred to as a field; another samples of a force field ar the electrical field around each electrical phenomenon and also the force field around each mass.) A magnetic flux will be visualised as consisting of lines of attractive force, or flux, originating at a pole and ending at a South Pole. This direction, from the north to the South Pole, is outlined because the direction of the magnetic flux.

Flux lines haven't any material existence; they're just a convenient thanks to visualize a magnetic flux. However, they will be incontestible physically. a way to try to to this can be to position a sheet of paper over a magnet and sprinkle iron filings on the paper. The iron filings can align themselves on flux lines and convey out the pattern of the magnetic flux. (Jiggling or sound the paper helps to bring out the pattern.) Another technique is to position little compasses at numerous points around a magnet. The compass needle aligns itself on a line of force. If the orientation of the needle is recorded at several locations, the pattern of the sphere can emerge.

Flux lines ne'er cross each other, and that they behave as if subject to 2 competitory forces: every line tries to shrink to the tiniest attainable length, however it's conjointly repelled by the neighboring lines. Thus, a north and a South Pole attract one another as a result of the lines between them try and shrink. within the case of like poles, the lines don't connect one pole to the opposite, and also the poles ar pushed apart as a result of every line is repelled by the neighboring lines and tries to place the maximum amount area as attainable between itself and its neighbors. Here again, it ought to be emphasised that the lines ar just a convenient model.

The strength of a magnetic flux refers to the force that a magnet, a bit of iron, or another check object feels at a specific purpose within the field. Strength is proportional to the concentration of the flux lines. wherever the lines ar targeted (close together), as within the region close to a pole, the sphere is strong; wherever the lines ar way apart, the sphere is weak.

Magnetic-field strength decreases speedily with distance from the magnet. The decrease obeys the inverse sq. law—that is, the strength is proportional to 1/r2, wherever r is that the distance from the magnetic pole. Doubling the space, as an example, reduces the strength to 1 fourth.

Atomic Basis of Magnetism. as a result of matter is created from atoms, and atoms ar charged nuclei enclosed by orbiting electrons, every atom could be a potential magnet. However, the orbital rotation of electrons produces solely a awfully weak magnetic flux. it's the spinning of the electrons as they orbit the atomic nucleus that offers materials magnetic properties. In most substances [*fr1] the orbiting electrons spin in one direction and also the spouse within the reverse direction, thereby canceling any magnetic result. In iron, however, of the fourteen electrons within the third shell (or orbit), the amount of electrons with positive spin doesn't equal the amount of electrons with negative spin. This makes every iron atom act sort of a little magnet; it possesses a property referred to as torsion. in an exceedingly piece of iron, once the magnetic moments ar all aligned within the same direction, the piece of iron as an entire becomes magnetic. This behavior of iron is named magnetism. Iron, nickel, and cobalt, among the alleged transition parts, and a number of other of the rare-earth parts (atomic numbers fifty seven through 71) ar labeled  magnetism as a result of they share iron's magnetic property. as a result of iron displays the strongest magnetism and is lowest in value, it's most typically wont to create magnets. (Several of the rare-earth parts become a lot of powerfully magnetic than iron below temperature.)

Not all iron bars ar magnets. The "atomic magnets," created by a web negatron spin, should be aligned so a majority of them ar orientating in an exceedingly explicit direction. Otherwise the atomic magnets can cancel one another, and also the bar won't be a magnet.

Magnetic properties ar full of temperature. the upper the temperature, the less magnetism there'll be in an exceedingly magnet, till all magnetization disappears at what's referred to as the temperature, or Curie point. The temperature is concerning 770° C (1420° F) for iron, 1120° C (2050° F) for metal, and 358° C (676° F) for nickel. (When a magnet cools, it once more becomes ferromagnetic; but, if it's a static magnet, it's to be remagnetized.)

Electricity and Magnetism. electrical and magnetic phenomena ar intimately connected. One cannot exist while not the opposite, and also the 2 sets of phenomena ar typically referred to as electromagnetism. as an example, each moving electrical phenomenon produces a magnetic flux around itself. as a result of an electrical current could be a flow of electrical charges, a current-carrying wire includes a magnetic flux around it. The magnetic flux lines of this field ar closed loops close the wire. Physicists have long used the "right-hand rule" to recollect the direction of this magnetic flux. Hold the proper hand within the hitchhiker's position: once the thumb points within the direction of the electrical current, the other, curled fingers can purpose within the direction of the magnetic flux. (We ar mistreatment the traditional definition of the direction of an electrical current: the direction is opposite to the direction during which the electrons ar flowing through the wire. an electrical current outlined during this manner typically is just referred to as an electrical current, or typically a standard current; an electrical current outlined as flowing within the same direction because the negatrons is named associate electron current.)

If a current-carrying wire is bent into a loop, the flux lines all bear the loop within the same direction; as a result a magnet is created. The magnet will be created abundant stronger if we tend to bend the wire into several loops—that is, into a spiral or coil—so that there's a bigger concentration of flux lines rummaging the coil. as a result of flux lines choose to bear iron instead of air or empty area, we will concentrate the lines even a lot of by inserting associate iron core into the coil. What we've got now's associate magnet. the nice advantage of associate magnet is that the sphere it creates will be turned on and off by turning this on and off. conjointly the magnetic flux (or poles) will be reversed by reversing the flow of current within the coil.

Magnetic Interactions. A magnet attracts associate unmagnetized piece of iron by turning it into a magnet briefly. as an example, once a magnet is brought close to associate iron or steel staple, the magnetic flux from the static magnet aligns a number of the atomic magnets within the staple, thereby inflicting the staple to become a brief magnet. This briefly magnetic  staple has its South Pole attracted (by manner of its magnetic field) to the pole of the static magnet, and also the staple attaches itself to the magnet. The staple, currently a magnet, will attract alternative paper clips within the same manner. once the staple is aloof from the magnetic flux, its atoms lose their alignment, and also the steel becomes demagnetized.

When electrons ar in motion, they produce a magnetic flux. Therefore, if associate negatron moves through a magnetic flux, the sphere created by the moving negatron can act with the magnetic flux that the negatron is moving through, and also the negatron are going to be deflected from its initial course. Physicists use a "left-hand rule" to indicate the interaction of those forces. The forefinger points within the direction of the magnetic flux (going from north to south); the center finger points within the direction of a positive particle's movement (or the direction from that a negative particle is moving); and also the thumb indicates the direction of the force to that the particle are going to be subjected. the ultimate direction of the particle is decided by the vector of speed|the speed|the rate} imparted by this force and also the initial velocity of the particle coming into the magnetic flux. This deflection of a charged particle (or of a beam of charged particles) is created use of in several devices. In associate microscope, as an example, a beam of electrons traveling on associate exhausted tube is deflected and targeted by magnet "lenses" within the type of coils round the tube. Particle accelerators (atom smashers) use huge magnets to manage the ways of charged particles. tv image tubes, oscilloscopes, and plenty of alternative devices conjointly create use of the deflection of a beam of charged particles by magnetic (and by electric) fields.

A region will be secure from magnetic fields by close it with iron or another magnetic material. The flux lines pass preferentially through the iron and avoid the realm within.