Applications of
Faraday's law
Contribution to Electromagnetic Theory
Faraday’s law is one of the four celebrated Maxwell’s equations
which synthesize the electromagnetic theory. According to Maxwell himself, his
mathematical work is a translation of Michael Faraday's earlier qualitative
ideas about lines of force. In addition, Faraday’s work motivated Maxwell to
think that in view of the symmetry in nature, the converse of Faraday’s law
also must be true i.e. Changing electric field must give rise to magnetic
field. This line of thinking led him ultimately to the concept of the
displacement current and extension of Ampere’s law to dynamic conditions which
is Maxwell’s significant contribution to the theory of electrodynamics.
Technological Applications
Faraday’s law gives rise to countless technological applications
too. The law has far-reaching consequences that have revolutionized the living
of mankind after its discovery. Faraday’s discovery of electromagnetic
induction has numerous industrial, technological, medical and other
applications. Some of them are briefed as follows
Transformers
Transformer can transform the levels of A.C. voltage and current
very easily. They are useful to transmit A.C. electricity over long distances
without much loss of power. At the generating station, voltage is increased to
hundreds of kV by using step-up transformers. The distribution system of power
line has to carry proportionately reduced current over long distances and power
loss in transmission lines is minimized. Afterwards, at the user end the
voltage is decreased to the 230 V (A.C. Mains) by using step-down transformers
for operating the household appliances, industrial machines etc.
Electrical Generators
A coil of wire spun in a magnetic field at a constant rate
produces electromotive force. Mechanical energy is converted to electrical
energy. In hydro-electric power plant the energy of falling water is used to
spin permanent magnets around a stationary loop of wire, to produce electrical
power from hydrolic power. Induction Welding
When an electrically conductive or a ferromagnetic sample is
placed in a high-frequency electromagnetic field of a coil carrying
radio-frequency electric current, the sample gets heated due to combination of
heat by magnetically induced currents called eddy currents and hysteresis. This
heat is useful for welding samples – even of nonmagnetic materials by
implanting metallic or ferromagnetic compounds in them.
Induction Cookers
A.C. flowing through the coil of copper wire - placed below a
cooking container - produces an alternating magnetic field. That magnetic field
induces a current in the electrically conductive container, produces heat in it
by Joule (I2R) heating effect. In addition there is some amount of heat due to
magnetic hysteresis in the ferromagnetic container also. Induction cookers are
faster, have better thermal efficiency and offer instantaneous control of
cooking energy.
Electromagnetic Flow Meters
A magnetic field is applied to electrically conducting fluids
flowing in electrically insulated pipes, an electromotive force proportional to
velocity is induced according to the principle of electromagnetic induction.
Used to measure velocity of blood, slurries etc.
Musical Instruments
Musical instruments like electric guitar, electric violin etc have
a pick-up device attached to them. It consists of a fine enameled copper wire
wound on a magnet. When the metal strings of the guitar are strung, the
vibrating string cuts the magnetic flux of magnet linking the coil due to which
electric current is induced in the pick-up’s coil. It is modulated by the mechanical
vibrations of the strings. This electrical signal is then amplified and
recorded by suitable devices. In addition the phenomena of electromagnetic
induction is also used in instruments and machines like Induction motors,
Induction Sealing, Audio video tapes, Hall effect meters, Faraday Disk etc.
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