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## Electromagnetic Dynamo

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### The connection with the topic in the course. Currents. Magnetic fieds. Electromagnetism. Basic theory of Dynamo. Currents & Magnetic Fields ... – PowerPoint PPT presentation

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Title: Electromagnetic Dynamo

1
Electromagnetic Dynamo
• Jing Hu
• Dan Wu
• JinHee(Ellen) Ahn
• Yuanyuan Zhang

2
The connection with the topic in the course
• Currents
• Magnetic fieds
• Electromagnetism
• Basic theory of Dynamo

3
Currents Magnetic Fields
• Hans Christian Oersted(1777-1851) was a physicist
and chemist who first discovered the
electromagnetism. He was the first person to
notice movements of a compass needle when it was
placed near electric fields (current carrying
wires). This was when he realized connections
between magnetism and electricity.

4
Currents Magnetic Fields
• The changes of the compass at different places
around the wire, proves that the magnetic field
circulates perpendicularly to the wire. When the
current moves upwards, the magnetic field move
towards the right. When the current moves
downwards, the magnetic field moves towards the
left.

5
Electromagnetic Induction
• After Oersted discovered how magnetism was
produced by current carrying wires, it was a
question if magnetism can produce electricity.
• The two physicist on the right discovered the
possibility in 1831. It was a coincidence that
they discovered what is now Faradays Law at the
same time because they were not aware of each
others work.

Joseph Henry (1797-1878) United States
6
Electromagnetic Induction
• Moving a magnet in or out of coils of
current-carrying wires can produce electricity.
• Electricity is produced by relative motion
between wire and magnetic field.
• Greater number of coils can produce more
voltage.
• More difficult to move magnet when there is
greater number of coil. Its because there is
greater resistance between magnetic field and
wire.

7
Generators and alternating current
• A simple generator.
• Electricity is generated with the same concept
create relative motion between a current carrying
wire and magnetic fields.
• Reverse position of wire and magnet electricity
exhibited when coil of wire rotate surrounded by
magnetic field. This method is more functional.

8
The history of electromagnetic generator
• In 1831-1832 Michael Faraday discovered that
a potential difference is generated between the
ends of an electrical conductor that moves
perpendicular to a magnetic field. He also built
the first electromagnetic generator called the
'Faraday disc', a type of homopolar generator,
using a copper disc rotating between the poles of
a horseshoe magnet. It produced a small DC
voltage, and large amounts of current. Its the
beginning of the modern dynamo.

9
Electrical generator
• In 1832 Hippolyte Pixii built an early form
of alternating current electrical generator,
based on the principle of magnetic induction
discovered by Michael Faraday In 1832 he built an
early form of alternating current electrical
generator, based on the principle of magnetic
induction discovered by Michael Faraday. It used
a permanent magnet which was rotated by a crank.
The spinning magnet was positioned so that its
north and south poles passed by a piece of iron
wrapped with wire. Pixii found that the spinning
magnet produced a pulse of current in the wire
each time a pole passed the coil. Furthermore,
the north and south poles of the magnet induced
currents in opposite directions. By adding a
commutator, Pixii was able to convert the
alternating current to direct current.

10
Theory of the Dynamo
amperage flow through LOAD 1 causes DYNAMO 1 to
act as a motor, driving DYNAMO 2 as a generator
and transferring excess power to the other side
onto COIL B.
• If LOAD 2 is greater than LOAD 1, the rotor will
spin the other direction, moving power from
Dynamo 2 to Dynamo 1.
rotor between the two dynamos can completely stop
moving. There are mechanical forces present due
through the respective Dynamos, but the driving
forces perfectly balance each other out.

11
reference
• http//www.siemon.com/uk/white_papers/images/06-05
-01-magnets3.gif
• http//www.sciencebuddies.org/mentoring/project_id
eas/Phys_img030.gif
• http//www.pbs.org/wgbh/nova/orchid/images/amat_fa