2. Submittedby~Pranav
Parashar
CERTIFICATE
This is to certify that the PHYSICS project titled
‘ELECTROMAGNETIC INDUCTION’ has been
successfully completed by PRANAV PARASHAR of Class
XII in partial fulfillment of curriculum of CENTRAL BOARD
OF SECONDARY EDUCATION (CBSE) in the year of
2015-2016.
3. INTERNAL EXAMINER TEACHER IN-CHARGE
ACKNOWLEDGEMENT
It gives megreatpleasureto expressmy gratitude towards our Physics
teacher MR. VIMAL KUMAR for his guidance, support and
encouragementthroughoutthedurationoftheproject. ThenI wouldlike
to thankmyparentsandfriends whohavehelpedmewiththeirvaluable
suggestionsandguidance has been helpful in various phases of the
completion of the project. Without their motivation and help the
successfulcompletion of this project would not have been possible.
Pranav Parashar
5. INTRODUCTION:
araday's law of induction is a basic law of electromagnetism that
predicts how a magnetic field will interact with an electric circuit to
produce an electromotive force (EMF). It is the fundamental
operating principle of transformers, inductors, and many types
of electrical motors and generators.
Electromagnetic induction was first discovered by Michael Faraday, who
made his discovery public in1831.It was discovered independently by Joseph
Henry in 1832.
Faraday explained electromagnetic induction using a concept he called lines
of force. These equations for electromagnetics are extremely important since
they provide a means to precisely describe how many natural physical
phenomena in our universe arise and behave. The ability to quantitatively
describe physical phenomena not only allows us to gain a better
understanding of our universe, but it also makes possible a host of
technological innovations that define modern society. Understanding
Faraday’s Law of Electromagnetic Induction can be beneficial since so many
aspects of our daily life function because of the principles behind Faraday’s
Law. From natural phenomena such as the light we receive from the sun, to
technologies that improve our quality of life such as electric power generation,
Faraday’s Law has a great impact on many aspects of our lives.
F
6. Faraday’s Law is the result of the experiments of the English chemist and
physicist Michael Faraday. The concept of electromagnetic induction was
actually discovered simultaneously in 1831 by Faraday in London and Joseph
Henry, an American scientist working in New York, but Faraday is credited for
the law since he published his work first . An important aspect of the equation
that quantifies Faraday’s Law comes from the work of Heinrich Lenz, a
Russian physicist who made his contribution to Faraday’s Law, now known as
Lenz’s Law, in 1834 (Institute of Chemistry).
Faraday’s law describes electromagnetic induction, whereby an electric field is
induced, or generated, by a changing magnetic field. Before expanding upon
this description, it is necessary to develop an understanding of the concept of
fields, as well as the related concept of potentials.
Faraday's first experimental demonstration of electromagnetic induction
(August 29, 1831), he wrapped two wires around opposite sides of an iron ring
or "torus" (an arrangement similar to a modern toroidal transformer) to induce
current. Based on his assessmentof recently discoveredproperties of
electromagnets,he expected that, when current started to flow in one wire,
a sort of wave would travel through the ring and cause some electrical
effecton the opposite side.He plugged one wire into a galvanometer, and
watched it as he connected the other wire to a battery. Indeed,he saw a
7. transient current (which he called a "wave of electricity") when he
connected the wire to the battery, and another when he disconnectedit.
This induction was due to the change in magnetic flux that occurred when
the battery was connected and disconnected.Within two months, Faraday
found several other manifestations of electromagnetic induction. For
example, he saw transient currents when he quickly slid a bar magnet in
and out of a coil of wires, and he generated a steady (DC) current by
rotating a copperdisk near the bar magnet with a sliding electrical lead
("Faraday's disk").
Figure 1 Faraday's First Experiment
Some physicists have remarked that Faraday's law is a single equation
describing two different phenomena: the motional EMF generated by a
magnetic force on a moving wire (see Lorentz force), and
the transformerEMF generated by an electric force due to a changing
magnetic field (due to the Maxwell–Faraday equation). James Clerk
Maxwell drew attention to this fact in his 1861 paper On Physical Lines of
Force. In the latter half of part II of that paper, Maxwell gives a separate
physical explanation for each of the two phenomena. A reference to these two
aspects of electromagnetic induction is made in some modern textbooks.
8. THEORY:
Magnetic flux:
The magnetic flux (often denoted Φ or ΦB) through a surface is the
component of the B field passing through that surface. The SI unit of
magnetic flux is the weber (Wb) (in derived units: volt-seconds), and
the CGS unit is the maxwell. Magnetic flux is usually measured with a
fluxmeter, which contains measuring coils and electronics that
evaluates the change of voltage in the measuring coils to calculate
the magnetic flux.
If the magnetic field is constant, the magnetic flux passing through
a surface of vector area S is
where B is the magnitude of the magnetic field (the magnetic flux
density) having the unit of Wb/m2
(Tesla), S is the area of the
surface, and θ is the angle between the magnetic field lines and
the normal (perpendicular) to S.
9. For a varying magnetic field, we first consider the magnetic flux
through an infinitesimal area element dS, where we may consider the
field to be constant
:
From the definition of the magnetic vector potential A and
the fundamental theorem of the curl the magnetic flux may also be
defined as:
where the line integral is taken over the boundary of the surface S,
which is denoted ∂S.
10. Law:
The most widespread version of Faraday's law states:
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.
Where is the electromotive force (EMF) and ΦB is the magnetic flux. The
direction of the electromotive force is given by Lenz's law.
This version of Faraday's law strictly holds only when the closed circuit is a
loop of infinitely thin wire, and is invalid in other circumstances as
discussed below. A different version, the Maxwell–Faraday
equation (discussed below), is valid in all circumstances.
For a tightly wound coil of wire, composed of N identical turns, each with
the same magnetic flux going through them, the resulting EMF is given by
When the flux changes—because B changes, or because the wire loop is
moved or deformed, or both—Faraday's law of induction says that the wire
loop acquires an EMF , defined as the energy available per unit charge that
travels once around the wire loop (the unit of EMF is the volt).Equivalently, it
is the voltage that would be measured by cutting the wire to create an open
circuit, and attaching a voltmeter to the leads.
According to the Lorentz force law (in SI units),
The EMF on a wire loop is:
11. where E is the electric field, B is the magnetic field (aka magnetic flux density,
magnetic induction), dℓ is an infinitesimal arc length along the wire, and
the line integral is evaluated along the wire (along the curve the coincident
with the shape of the wire).
The Maxwell–Faraday equation states that a time-varying magnetic field is
always accompanied by a spatially-varying, non-conservative electric field,
and vice-versa. The Maxwell–Faraday equation is
Where is the curl operator and again E(r, t) is the electric field and B(r, t)
is the magnetic field. These fields can generally be functions of position r and
time t.
The four Maxwell's equations (including the Maxwell–Faraday equation),
along with the Lorentz force law, are a sufficient foundation to
derive everything in classical. Therefore it is possible to "prove" Faraday's law
starting with these equations. Faraday's law could be taken as the starting
point and used to "prove" the Maxwell–Faraday equation and/or other laws.)
Devices that work on electromagnetic
induction:
12. The principles of electromagnetic induction are applied in many devices and
systems, including:
Current clamp
Electrical generators
Electromagnetic forming
Graphics tablet
Hall effect meters
Induction cookers
Induction motors
Induction sealing
Induction welding
Inductive charging
Inductors
Magnetic flow meters
Mechanically powered flashlight
Pickups
Rowland ring
Transformers
Wireless energy transfer
