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.

Michael Faraday (1791-1867) United Kingdom
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

• When LOAD 1 is greater than LOAD 2, the increased
  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.
• When LOAD 1 and LOAD 2 are equally balanced, the
  rotor between the two dynamos can completely stop
  moving. There are mechanical forces present due
  to the current from LOAD 1 and LOAD 2 passing
  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
  raday.jpg
• http//www.nndb.com/people/671/000096383/joseph-he
  nry-1-sized.jpg
• http//sol.sci.uop.edu/jfalward/physics17/chapter
  9/generator.jpg
• http//en.wikipedia.org/wiki/Dynamo
• http//en.wikipedia.org/wiki/Electric_current
• Text book