Electromagnetic Induction and AC
Electromagnetic induction is the phenomenon in which an electromotive force (EMF) is produced in a conductor when magnetic flux changes around it. This phenomenon was first discovered by Michael Faraday in the 1830s.
Induced current: The electric current induced in a coil or closed loop due to electromagnetic induction is called induced current.
Induced EMF: The EMF induced in a conductor or coil due to electromagnetic induction is called induced EMF.
Magnetic flux (Φ):
The total number of magnetic field lines passing through a surface perpendicularly is called magnetic flux. Magnetic flux is a scalar quantity and is measured in Weber (Wb) in the International System of Units (SI).
Mathematically, magnetic flux (Φ) is defined as the dot product of the magnetic field vector (B) and the surface area vector (A) through which the field lines pass. For a uniform magnetic field, the formula is Φ = B * A * cos(θ), where θ is the angle between B and A.
Table of Contents
INDEX – EMI and AC
| Chapter–6: Electromagnetic Induction Electromagnetic induction; Faraday’s laws, induced EMF and current; Lenz’s Law, Self and mutual induction. | |
| Chapter–7: Alternating Current Alternating currents, peak and RMS value of alternating current/voltage; reactance and impedance; LCR series circuit (phasors only), resonance, power in AC circuits, power factor, wattless current. AC generator, Transformer. |
Faraday’s laws:
Faraday’s laws refer to two important principles of electromagnetic induction, discovered by Michael Faraday in the early 19th century, which are fundamental and help in understanding how a changing magnetic field induces an electric current in a conductor.
Faraday’s First Law of Electromagnetic Induction:
The first law states that when magnetic flux changes around a coil, an electromotive force (EMF) is induced in it, and it is lost as long as the flux change is taking place.
Faraday’s Second Law of Electromagnetic Induction:
The second law states that the magnitude of the induced EMF in a conductor is directly proportional to the rate of change of the magnetic flux through the conductor.
Mathematically, it can be expressed as EMF = – dΦ/dt,
where EMF is the induced electromotive force, and dΦ/dt is the rate of change of magnetic flux. Here negative sign indicate that emf is induced due to opposition of cause due to which emf is induced.
Lenz’s Law: Determination of the Direction of Induced EMF According to Lenz’s law, The direction of the induced EMF (voltage) is in such a way that it opposes the cause due to which EMF is induced.
Applications Electromagnetic induction:
Electromagnetic induction has numerous practical applications in our daily lives. The basic principle behind the working of generators, transformers, and electric motors, which are essential components in power generation and distribution systems.
Eddy current
Eddy current is the current produced in a metallic plate as a result of a change in magnetic flux around it.
The current is so named because it is produced in the form of eddies or whirlpools.
The direction of eddy currents can be determined using Lenz’s law or Fleming’s right-hand rule.
If eddy currents are undesirable, then they cause energy losses.
Although eddy currents cause energy losses, they have some important applications as well.
Induction furnace: with the help of a magnetic coil, magnetic flux is changed around a metallic plate. due to electromagnetic induction eddy current is produced in metallic plate which causes heating of it and metal starts melting.
What is wattless current?
Answer: The current due to which power dissipation is zero is called wattless current. The current component 
due to which power consumption is zero, is known as wattless current.
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