Faraday's Law, Faraday's laws derivation and faraday's Law application and lenz's law

 Faraday’s Law of Electromagnetic induction

:-  Great experiment physicist and chemist

:-  1791- 1867

:-  Contribution to early electricity include:

     - Invention of motor, Generator, and Transformer

     - Electromagnetic Induction

     - Laws of electrolysis: A method of separating bonded element and

       Compounds by passing an current through them.

 

Electromotive Force (EMF) Produced by Changing Magnetic Field, 1

:-  A loop of wire is connected to a sensitive ammeter.

:-  When a magnet is moved toward the loop, the ammeter deflects.

Electromotive Force (EMF) Produced by Changing Magnetic Field, 2

:-  When the magnet is held stationary, there is no deflection of the ammeter.

:-  Therefore, there is no induced current

     :- Even though the magnet is in the loop.

 

Electromotive Force (EMF) Produced by Changing Magnetic Field, 3

:-  The magnet is moved away from the loop.

:-  The ammeter deflects in the opposite direction.

 

Faraday’s First Law

 Faraday’s Law of induction states that “ the emf induced in a circuit is directly proportional to the time rate of change of the magnetic flux through the circuit”

Mathematically,

 

Faraday’s Second Law

:-  Remember ϕB is the magnetic flux through the circuit and is found by

 

:-  If the circuit consists of N loops, all of the same area, and id ϕB is the flux through one loop, an emf is induced in every loop and Faraday’s Law becomes.

 

                            Faraday’s Law Example

:-  Assume a loop enclosing an area A lies in a uniform magnetic field B

:-  The magnetic flux through the loop is ϕB = B.A cos(Φ)

:-  The induced emf is

 

               Way of Induced an EMF

:-  The magnitude of B can change with time.

:-  The area enclosed by the loop can change with time.

:-  The angle (Φ)  between B and the normal to the loop can change with time.

:-  Any combination of the above can occur.

 

                                         Lenz’s law

:-  Faraday’s law indicate that the induced emf and the change in flux have opposite algebraic signs.

:-  The has a physical interpretation that has come to be known as Lenz’s Law.

:-  Develops by German physicist Heinrich Lenz

 

                              Lenz’s Law, cont.

:-  Lenz’s Law: - The induced current in a loop is the direction that creates a magnetic field that opposes the change in magnetic flux through the area enclosed by the loop.

:-  The induced current tends to keep the original magnetic flux through the circuit from changing.

 

Application of Faraday’s Law

Electric Generator - An electric conductor, like a copper wire, is moved through a magnetic field, which causes an electric current to flow (be induced) in the conductor.

 

Generator -  Electric generator take in energy by work and transfer it out by electrical transmission.

The ac generator consist of a loop of wire rotated by some external means in a magnetic field.

 

Application of Faraday’s Law

Pickup coil - The coil is placed near the vibrating string and causes a portion of the string to become magnetized.

When the string vibrate at the same frequency, the magnetized segment produces a changing flux through the coil.

The induced emf is fed to an amplifier.

 

Application of Faraday’s Law

Transformer - An ac one winding creates a time- varying magnetic flux in the core, which induced a voltage in the other winding.

 

 Application of Faraday’s Law

Yamanashi Maglev - The magnetized coil running along the track, called a guideway, repels the large magnet on the train’s undercarriage, allowing the train to levitate between 0.39 and 3.93 inches ( 1 to 9cm ) above the guideway.