A magnet can be broken into many pieces,
and each piece becomes a new magnet with its own North Pole and South Pole.
MAGNETIC FLUX
(Φ)
The invisible lines of force that make
up the magnetic field are known as magnetic flux. It
is denoted by Φ and its unit is weber.
MAGNETIC FIELD
A magnetic field is the region around
the magnet where force of attraction and repulsion takes place.
MAGNETIC POLE
This is a region where the external
magnetic effects of magnet are concentrated or it is the point where the
strength of magnet is maximum.
UNIT MAGNETIC POLE
The unit of magnetic pole strength equal
to the strength of a magnetic pole that repels a similar pole with a force of
one dyne, the two poles being placed in a vacuum and separated by a distance of
one centimeter.
MAGNETIC FLUX DENSITY (B)
Magnetic flux density at any point in a
magnetic field is the magnetic flux passing per unit area at that point. It is
denoted by B and its unit is Tesla or Weber / metre2
MAGNETIC FIELD INTENSITY (H)
The magnetizing force or the magnetic
field intensity is defined as the magnetic motive force per unit length of the
magnetic flux path. It is denoted by H and its unit is ampere-turn / metre.
MAGNETO MOTIVE FORCE (M.M.F)
The force which drives the magnetic flux
through a magnetic circuit is called the magnetic motive force. It is produced
by passing electric current through a coil of wire have number of turns. It is
measured in ampere-turns.
RELUCTANCE (S)
The property of a magnetic circuit which
restricts the establishment of magnetic flux is called reluctance. It is
denoted by S and its unit is ampere-turns / weber.
PERMEANCE (P)
The reciprocal of reluctance of a
magnetic circuit is called as permeance. It is denoted by P and Its unit is
weber / ampere-turn.
MAGNETIC CIRCUIT
A combination of media, mainly comprising
ferromagnetic substance, forming a close circuit though which a flux of
magnetic induction may pass.
SIMPLE MAGNETIC CIRCUIT
A simple magnetic circuit is made up of
a single magnetic material. Thus such a circuit reflects the magnetic
properties of the materials used.
COMPOSITE MAGNETIC CIRCUIT
It is a magnetic circuit which comprises
of two or more elements whose magnetic properties are different.
PERMEABILITY (µ)
It is the ratio between flux density to
flux intensity. It is denoted by µ. µ = B / H. it has no unit, as it is a
ratio.
ABSOLUTE PERMEABILITY (µ0)
Absolute permeability of a medium is
given by the ratio of flux density to magnetizing force at a point in the
medium µ0.
RELATIVE PERMEABILITY (µR)
Relative permeability of a medium is
given by the ratio of absolute permeability of the medium to the absolute
permeability of vacuum. It is also equal to the ratio of flux density produced
in a medium to the flux density produced in vacuum by the same magnetizing
force µr.
SERIES MAGNETIC CIRCUIT
A closed magnetic path consisting of
different sections of varying permeabilities and physical dimensions but having
the same magnetic flux is called a series magnetic circuit.
PARALLEL MAGNETIC CIRCUIT
The flux created by the Magneto Motive
Force (M.M.F) acting in the magnetic circuits gets divided into two or more
branches/portions of the magnetic core. The fluxes in these branches may be
different, but the magnetic potential drops across the branches may be
different, but the magnetic potential drop across the branches remains the
same. Such a magnetic circuit is called parallel magnetic circuit.
MAGNETIC CORE
A part of magnetic circuit surrounded by
a coil.
MAGNETIC POTENTIAL DROP
When a magnetic flux Ф is established in
magnetic circuit of reluctances S there is a always a magnetic potential drop M
along direction of the flux.
The magnetic potential drop is the product of the
flux and reluctance. M = S x Ф.
MAGNETIC LEAKAGE
A small part of the flux completes its
path through air rather than through the core, which is called as leakage
reactance or magnetic leakage.
MAGNETIC LEAKAGE REACTANCE
Reactance of the transformer due to
leakage (primary flux not linking secondary) is called as leakage reactance of
transformer.
MAGNETIC LEAKAGE CO-EFFICIENT
The flux that follows in an undesired
path is called leakage flux. The ratio of total flux to useful is called
leakage flux co-efficient.
RETENTIVITY
A magnetic material can retain the
magnetism even after the removal of the magnetising source. This property of
the magnetic materials is called retentivity.
RESIDUAL MAGNETISM
The flux that remains in a temporary
magnet after, it is removed from a magnet field is called residual magnetism.
MAGNETIC SATURATION
A magnetic material is saturated when an
increase in m.m.f. no longer increases the flux in the material.
EDDY CURRENT
Eddy current are those which are
produced or induced in the masses of metals, whenever these metals are moved in
magnetic field, or the magnetic field moves through the metals. The direction
of the eddy currents is always in opposite direction to the cause (motion) to
produce them.
MAGNETIC HYSTERESIS
The lagging of the magnetic induction
with respect to magnetizing force is called magnetic hysteresis.
MAGNETIC SHIELDING
Transformers and choke produce strong
magnetic in the space around the equipment. These magnetic field affect the
performance of the equipment which are situated in close vicinity. Such a
magnetic field may cause humming in radio receivers and also affects the
readings of the measuring instruments. A hallow piece of ferromagnetic material
is used to enclose the equipment which acts a magnetic shielding. The
ferromagnetic material has high permeability.
SOLENOID
A coil usually of tubular form for
producing a magnetic field.
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