 # Electromagnetism By Bao Tran. Electromagnetic induction  Electromagnetic induction is a process in which a conductor cuts through a stationary magnetic.

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Electromagnetism By Bao Tran

Electromagnetic induction  Electromagnetic induction is a process in which a conductor cuts through a stationary magnetic field lines (or conductor placed in a changing magnetic field).  The magnetic field lines cause the production of a voltage across the conductor.  The voltage produced in called induce EMF and causes current called induce current.

Electromagnetic induction (cont.)  Electromagnetic Induction was first discovered way back in the 1830’s by Michael Faraday.  He noticed that when he moved a permanent magnet in and out of a coil or a single loop of wire it induced an EMF, in other words a voltage, which therefore a current was said to produce.

Fleming’s Right Hand Rule  The rule of Fleming helps us to predict the direction of induce current relative to the motion of conductor.

A.C Generator  Power stations create alternating current using electromagnets rather than permanent magnets to create the magnetic field, then a rotating coil is inserted between these magnetic fields.  When the coil is rotating in a magnetic field, the electromagnetic induction results in an induced current through the loop. In this way, mechanical energy is converted to electrical energy.

A.C Generator (cont.)  The graph below shows the changing alternating current with time during the one cycle of rotation. When the rotating coil is in vertical positions, its current or voltage produced is zero. The current or voltage is maximum when the coil is in horizontal positions.

A.C Generator (cont.)  Dynamo:  A dynamo is a simple current generator. The change in magnetic flux through the coil induce an alternating current in the wires.  The frequency of the electricity depends on the speed of the bicycle.

Transformer  A transformer makes use of Faraday’s law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages. The size of the voltage in the secondary coil is depend on the ratio of the number of turns wrapped around the other side of the core.

Transformer (cont.)  REMEMBER. - If the input voltage is greater than the output voltage, the transformer is called a step-down transformer, however, if the output voltage is greater than the input voltage, the transformer is called a step-up one.

D.C motor  When electric current passes through a coil in a magnetic field, the magnetic force produces a torque which turns the DC motor.  If the direction of the current, or the poles of the magnet, are reversed, rotation will proceed in the opposite direction.

Cathode-ray oscilloscopes  Cathode rays were discovered in late 1800 by J.J. Thomson.  There are consists of stream of electrons emitted from heated cathode.  Anode, a positive terminal attracts the electrons from the cathode. The hole in the anode allows the electron to pass through it creating a beam of electrons shoots out in forward direction. The process is described as an electron gun.

Bibliography http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/transf.html http://ap-physics.david-s.org/cathode-ray-oscilloscopes/ http://www.electronics-tutorials.ws/electromagnetism/electromagnetic- induction.html http://ap-physics.david-s.org/electromagnetic-induction/ http://ap-physics.david-s.org/a-c-generator/ http://ap-physics.david-s.org/transformer/ http://ap-physics.david-s.org/d-c-motor/ http://ap-physics.david-s.org/cathode-ray-oscilloscopes/ http://electrical4u.com/dc-motor-or-direct-current-motor/ http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html

THANK YOU!

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