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Introduction
Electromagnetic induction is the phenomenon of generating varying magnetic fields through electric current. This phenomenon was invented by Michael Faraday. He performed this experiment with the help of a conductor, which is placed in a moving magnetic field. He noticed that the magnetic fields were constantly changing. The theory of electromagnetic induction is a practical utility. The experiments conducted by Micheal Faraday and Henry lead to many innovations such as generators and transformers.
Inductance is the property of an electrical conductor where it opposes the current flowing through it.
Magnetic flux
Magnetic flux is calculated as Φ=BA cos θ, where θ is the angle between magnetic field B and cross-section area A. It is defined in the same direction in which electric flux is defined.
Faraday law of induction
According to Faraday’s law of induction, the value of induced emf in a circuit is the same as the time rate of change of its magnetic flux. Mathematically, it is calculated as follows:
Where E is induced voltage and N number of turn of coil, is change in magnetic flux and t is a small time interval.
In this equation, the -ve sign shows its direction in the closed-loop.
Lenz’s law and conservation of energy
According to Lenz’s law, the polarity of induced emf has the property to produce a current which opposes the change in the magnetic flux. This law was proposed by physicist Heinrich Lenz. It calculates the polarity of the induced emf.
Electromagnetic spectrum
The electromagnetic spectrum covers the entire range of EM radiations. Humans can only see a specific range of the spectrum. The entire distribution is done according to the frequency and wavelength of electromagnetic waves. An EM wave is produced when the particles are accelerated when they get in contact with an electric field.
The electric field and magnetic field of an EM wave are perpendiculars (at 90 degrees) to each other. They are also perpendicular to the wave itself. The velocity of an EM wave is 3.00 x 108 ms-1 in a vacuum.
Electromagnetic wave examples-
Radio waves
Microwave
X-ray
Gamma-ray
Ultraviolet
Eddy currents
According to an observation, when bulk pieces of conductor material are kept near a changing magnetic flux, it produces induced current. These currents produced in the material are known as eddy currents. Eddy currents have both advantages as well as some disadvantages. The disadvantage is that there is heat loss during cycling eddy currents mainly because of the friction in magnetic circuits. Eddy currents can be minimised using electrically insulated thin laminated steel sheets.
Inductance
Inductance majorly depends on the geometry of the coil and the properties of that material. It is a scalar quantity only having value, not direction. Its SI unit is Henry commonly used as H.
Mutual inductance
Mutual inductance is the main operating principle of generators, motors, and transformers. Any electrical device having components that tend to interact with another magnetic field also follows the same principle. The interaction is usually brought about by a mutual induction where the current flowing in one coil generates a voltage in a secondary coil. The mutual inductance between two coils having N1 and N2 turns respectively is:
Where
ℓ is the length of the coil in metres
µo is the permeability of free space (4π×10-7)
N1 is in the number turns in primary coil
N2 is the number of turns in secondary coil
A is in the cross-sectional area in m2
µr is the relative permeability of the soft iron core
Applications of electromagnetic induction
Electromagnetic induction in AC generators- The AC generator uses Faraday’s law of induction. When the coil is turned, magnetic flux changes through the coil. Due to this, emf is induced. Hence it acts as a generator.
Electric transformers- An electric transformer utilises electromagnetic induction to alter the voltage of electric current. It happens when a moving conductor is placed within the magnetic field.
Magnetic flow metre- It uses the Faraday law of induction. A magnetic flow metre is used to calculate the velocity of conductive liquids flowing through a pipe.
Conclusion
The magnetic flux is the number of magnetic field lines passing through a closed area which is defined as follows. Magnetism and current are always related to each other. This was proved by Faraday and Henry in around 1830.
Electric currents are induced in a closed circuit loop so that they can oppose the changing magnetic flux associated with it. This is because of the law of conservation of energy which states that energy can neither be lost nor created. It only transforms the arm from one form to another.
Physicist Faraday proposed the laws of induction which affirm that the emf induced in a coil having N number of turns is directly related to the rate of change of flux through it.
Lenz’s law tells that when polarity is induced in a material due to the induced emf, it produces a current which opposes the change in magnetic flux.
The electric current setup in a material kept near a magnetic field is known as eddy currents. Inductance in a material is the ratio of flux-linkage to current.
