Faraday's law of induction
Qianmeng Gu(qxg5019)
Linnan Zhang(lqz5068)
Ying Ye(yoy5069)
We all know today is an age of electricity.
We enjoy the benefit the electricity
provides us everywhere.
• Long time ago, people burn woods,
coals and petroleum to generate
energy. Until 1800,Alessandro Volta
invented the first true battery which
came to be known as the Voltaic Pileconsisted of pairs of copper and zinc
discs piled on top of each other,
separated by a layer of cloth or
cardboard soaked in brine. This enable
human generate and utilize electricity.
People used chemical cell to transfer
chemical energy into electricity
Here comes a problem:
Voltaic Pile could not generate a
large amount of electricity,
therefore electricity still could
not be used widespread.
1831, Faraday and his Law of
Induction made the mass
production of electricity possible.
Instead of chemical energy, Law of
induction allow human to change
mechanical energy into electricity.
The predominant theory before
Law of induction
In 1820, Danish physicist and chemist, Hans
Christian Ørsted discovered the phenomenon of
In 1821 Faraday, Davy and William built
homopolar motor-which made continuous circular
motion from the circular magnetic force around a
wire and a wire extending into a pool of mercury
with a magnet placed inside that would rotate
around the magnet if supplied with current from a
chemical battery. This is foundation of modern
electromagnetic technology
Faraday was an English chemist and physicist
(or natural philosopher, in the terminology of
the time) who contributed to the fields of
electromagnetism and electrochemistry.
Faraday is best known for his work regarding
electricity and magnetism. His first recorded
experiment was the construction of a voltaic
pile with seven halfpence pieces, stacked
together with seven disks of sheet zinc, and
six pieces of paper moistened with salt water.
With this pile he decomposed sulphate of
magnesia (first letter to Abbott, 12 July
Faraday's law of induction
For the relationship between a time-varying
magnetic field and an induced electric field
In physics, a quantitative relationship between a
changing magnetic field and the electric field created
by the change, developed on the basis of
experimental observations made in 1831 by the
English scientist Michael Faraday.(Shown by the
right side picture)
Faraday discovered that, whenever the magnetic
field about an electromagnet was made to grow and
collapse by closing and opening the electric circuit of
which it was a part, an electric current could be
detected in a separate conductor nearby. Moving a
permanent magnet into and out of a coil of wire also
induced a current in the wire while the magnet was
in motion. Moving a conductor near a stationary
permanent magnet caused a current to flow in the
wire, too, as long as it was moving.
For the special case of a coil of wire, composed of N loops
with the same area, the equation becomes
The fundamental principles of electricity
generation is still used today!
 Faraday constructed a homopolar generator, now
also known as a Faraday disk, which produces a
relatively weak direct current (DC).
 This has been superseded by alternating current
(AC) electrical generators, which power the
machinery of the modern world.
 electricity is generated by the movement of a loop
of wire, or disc of copper between the poles of a
 This generates a current proportional to the rate
of rotation, which can power a small light bulb.
The disk can be rotated in either direction.
 However, this design was inefficient
 There are many other technologies that can be
and are used to generate electricity such as solar
photovoltaic and geothermal power.
 convenience of mobile communications
II. Microphone
III. Gramophone
 Mechanically-powered flashlight
This concept has many far-reaching ramifications that touch our lives in many
 Revealed the relationship of electricity and magnetic field
 Convenience of daily mobile communications
 Electricity to power our homes
 Long distance transmission of electricity became possible.
We can all appreciate the profound impact Faraday’s Law has on us.
Thank you for your attention
Blinder, S. M. (n.d.). Wolfeam Demonstrations Project. Retrieved Feb 20, 2012,
from http://demonstrations.wolfram.com/FaradayDiskDynamo/.
Electricity generation. (n.d.). Retrieved 02 10, 2012, from
Logan, A. (n.d.). Faraday's law of electromagnetic induction. Retrieved 02 11,
2012, from

similar documents