How Electromagnetism was discovered used and who pioneered it
Michael Faraday was an English scientist contributed to the study of electromagnetism and electrochemistry. The discoveries include the principles underlying electromagnetic induction, diamagnetism and electrolysis.
Born: 22 September 1791, Newington Butts, London, United Kingdom
Died: 25 August 1867, Hampton Court Palace, Molesey, United Kingdom
Awards: Royal Medal, Bakerian Lecture, Copley Medal, Rumford Medal, Albert Medal
Michael Faraday produce an electric current from a magnetic field, invented the first electric motor and dynamo, demonstrated the relation between electricity and chemical bonding, discovered the effect of magnetism on light, and discovered and diamagnetism.
Michael Faraday is generally credited with the discovery of induction in
1831, and James Clerk Maxwell mathematically described it as Faraday's law of induction. Lenz's law describes the direction of the induced field. Faraday's law was later generalized to become the Maxwell-Faraday equation.
Electromagnetic induction has found many applications in technology, including electrical components such as inductors and transformers, and devices such as electric motors and generators
According to Faraday’s laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field, an emf gets induced in the conductor
Faraday’s Laws of Electromagnetic Induction:-
Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field
- First Law: -
Whenever a conductor cuts magnetic flux , an e.m.f is induced in that conductor. Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field.
Mathematically it is written as:
Where E is the electromotive force (EMF) and ΦB is the magnetic flux.
- Second Law:-
The magnitude of the induced e.m.f is equal to the rate of change of flux linkages.
Now, we describe the explanation of induced e.m.f in a coil.
Let, N= No. of turns of a coil,
Φ1= Initial value of magnetic flux which cuts the coil,
Φ 2= Final value of flux in time t seconds.
flux-linkages is meant the product of number of turns by flux linked with the coil,
So, The initial flux linkages = N φ1
And final flux linkages = N φ2,
According to Faradays law of electromagnetic induction, the induced e.m.f is the rate of change of flux linkage.
Therefore, The induced e.m.f (e)=(NΦ2-NΦ1)/t Wb/ Sec, or Volt
Or, e= N (Φ2-Φ1)/t Volt,
In the differential from, we get ,
e = d/dt(NΦ) Volt
e = NdΦ/dt volt
Faraday's law of induction
The longitudinal cross section of a solenoid with a constant electrical current running through it. The magnetic field lines are induced indicated, with their direction are shown by arrows.
The magnetic flux 'density of field lines'.
Faraday's law of induction makes use of the magnetic flux ΦB through a region of space enclosed by a wire loop.
Definition of Electrolysis
Electrolysis is the movement of electricity through an electrolyte, with ions moving to the cathode to get reduced, and anions moving towards the anode to get oxidized. An electrolyte is a liquid that conducts electricity.
Faraday’s first law
According to this law, “The amount of substance liberated at an electrode is directly proportional to the quantity of electricity passed”.
or, Where W or M = amount of substance liberated in gram.
Q = quantity of electricity passed in coulomb.
Since Q = I.t
Where I = Current in ampere
and t = time in seconds
where Z = proportionality constant, called electrochemical equivalent.
If I = 1 ampere and t = 1 second then Z = W Therefore electrochemical equivalent may be defined as,
“The mass of substance (in grams) liberated at the electrode on passing current of 1 ampere for 1 second or on passing 1 coulomb of electricity is called electrochemical equivalent of the substance”.
- Faraday’s second law:
According to this law, “if same quantity of electricity is passed through different electrolytes, then the amount of substances liberated at the respective of electrodes are in the ratio of their equivalent masses”.
Suppose three cells containing HCI, solutions are connected in series. If same quantity of electricity is passed through these cells, then the amount of hydrogen, silver and copper deposited at the respective cathodes is in the ratio of their equivalent mass.
Electrical transformer/ Eddy Currents Circulating in a Transformer
When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, d ΦB / d t.
Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF. If the two ends of this loop are connected through an electrical load, current will flow.
The changing magnetic flux in the iron core of a transformer will induce an emf, not only in the primary and secondary windings, but also in the iron core.
The iron core is a good conductor, so the currents induced in a solid iron core. the current in the primary coil required to produce a given B field is increased, so the hysteresis curves are fatter along the H axis.
Working of Generators:
Generators are basically coils of electric conductors, normally copper wire, that are tightly wound on a metal core and are mounted to turn around inside an large magnets.
An electric conductor moves through a magnetic field, the magnetism will interface with the electrons in the conductor to induce a flow of electrical current inside it.
The conductor coil and its core are called the armature, connecting the armature to the shaft of a mechanical power source, for example an motor, the copper conductor can turn at exceptionally increased speed over the magnetic field.
The point when the generator armature first starts to turn, then there is a weak magnetic field in the iron pole shoes.
As the armature turns, it starts to raise voltage. Some of this voltage is making on the field windings through the generator regulator. This impressed voltage builds up stronger winding current, raises the strength of the magnetic field. The expanded field produces more voltage in the armature.
Types of Generators:
The generators are classified into types.
According to Faraday’s laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field, an emf gets induced in the conductor. The magnitude of induced emf can be calculated from the emf equation of dc generator.
If the conductor is provided with the closed path, the induced current will circulate within the path. In a DC generator, field coils produce an electromagnetic field and the armature conductors are rotated into the field.
Thus, an electromagnetically induced emf is generated in the armature conductors. The direction of induced current is given by Fleming’s right hand rule
Working of DC generator
According to Fleming’s right hand rule, the direction of induced current changes whenever the direction of motion of the conductor changes.
An armature rotating clockwise and a conductor at the left is moving upward. When the armature completes a half rotation, the direction of motion of that particular conductor will be reversed to downward. Hence, the direction of current in every armature conductor will be alternating. You know how the direction of the induced current is alternating in an armature conductor.
But with a split ring commutator, connections of the armature conductors also gets reversed when the current reversal occurs. Thus we get unidirectional current at the terminals.
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