Electromagnetic induction refers to the production of a voltage
or a potential difference across a conductor when it is exposed to a changing magnetic
field. The name of Faraday is generally acknowledged with the discovery of induction.
We first discuss the terms which will be used frequently in this topic and later
move on to the Faraday Law of electromagnetic Induction.
Flux: Flux is defined as the rate of flow of a property per unit
area. For example, the magnitude of a river's current which gives the quantity
of water flowing through a cross-section of the river each second is a kind of flux.
Emf: Emf is an abbreviation of electromagnetic force which is
the voltage developed by any source of electrical energy such as a battery. It is
denoted by ℰ and is measured in volts. The EMF is also given by the rate of change
of the magnetic flux:
ℰ = - dφB/ dt,
where ℰ is the electromagnetic force Emf in volts and ΦB is
the magnetic flux.
Faraday's laws of electromagnetic induction is a basic law
of electromagnetism which describes the interaction of a magnetic field with an
electric circuit to produce an emf I. It is the prime operating principle of various
kinds of motors and generators.
Christian Oersted’s discovery of magnetic field around a current carrying conductor
was quite accidental. If a flow of electric current can produce a magnetic field
then why can't a Magnetic field produce an electric current? While searching
for an answer to this Michel Faraday ended up inventing generators.
We now discuss in detail the Michael Faraday Law:
Relationship between Induced Emf and Flux
In this experiment Faraday took a magnet and a coil and connected a galvanometer
across the coil. In the beginning the magnet is at rest so there is no deflection
in the galvanometer and hence the needle of galvanometer is at center or zero position.
When the magnet is moved toward the coil, the needle of galvanometer deflects in
one direction. When the magnet is held stationary at that position, the needle of
galvanometer returns back to zero position. Now when the magnet is moved away from
the coil , there is some deflection in the needle but in opposite direction and
again when the magnet becomes stationary at that point with respect to coil , the
needle of galvanometer return back to zero position.
Also if the magnet is held stationary and the coil is moved away and towards the
magnet, the galvanometer shows deflection in a similar manner. It is also observed
that faster the change in the magnetic field, the greater will be the induced emf
or voltage in the coil.
The induced electromotive force in any closed circuit is equal to the negative
of the time rate of change of the magnetic flux through the circuit. This version
of the Faraday’s law is valid only when the closed circuit is a loop of indefinitely
Application of Electromagnetism in Physics (including the Faraday’s Law):
Faraday’s Law is a fundamental law of electromagnetism. This law has widespread
applications in various fields including industries, electrical machines etc. some
of the major ones are listed below:
· Electrical Transformers
This is a static device which is used for increasing or decreasing thhe voltage
or current. It has its applications in generating station, transmission and distribution
system. The transformer works on Faraday's law.
· Electrical Generators
The basic working principle of electrical generator is Faraday's law of mutual
induction .Electric generator is used to convert mechanical energy into electrical
· Induction Cookers
The Induction cooker also works on principle of mutual induction. When current
flows through the coil of copper wire placed below a cooking container, it produces
a changing magnetic field. This alternating or changing magnetic field induces an
emf and hence the current in the conductive container.
· Electromagnetic Flow Meters
It is used to measure velocity of blood and certain fluids. When a magnetic field
is applied to electrically insulating pipe in which conducting fluids are flowing
then according to Faraday's law an electromotive force is induced in it. This
induced emf is proportional to velocity of fluid flowing.
· Musical Instruments
It is also used in musical instruments like electric guitar, electric violin etc.