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Electromagnetic induction gives an idea about the generation and transfer of electrical energy. It is among the most important concepts in electromagnetism. Michael Faraday in 1831 first explained this phenomenon. The event defines how a change in the magnetic field within a closed loop creates an electromotive force (EMF) or voltage across that loop. Electromagnetic induction forms the basic principle behind most electrical devices, including transformers, electric motors, generators, etc.
Electromagnetic Induction and Alternating Currents is one of the important chapters for Class 12 students, as it has a lot of topics that are crucial for board exams. Students should have a clear understanding of the subject and should practice with some important questions, which will benefit them in the exams. So, in this context, we will focus on some Class 12 important questions on electromagnetic induction that occur in exams quite often along with their explanations.
PREMIUM EDUCART QUESTIONS
(Most Important Questions of this Chapter from our 📕)
In the table given below, we have provided the links to Electromagnetic Induction Class 12 Important Questions PDFs for Physics Chapter 6. You can download them without having to share any login info.
The section below will cover the most important questions asked in the Class 12 Electromagnetic Induction.
Faraday's laws of electromagnetic induction are important for understanding how an electromotive force (EMF) is induced in a conductor when the magnetic field changes. There are two main laws:
First Law (Faraday's Law of Induction): It indicates that whenever the magnetic flux changes in the coil, then it generates an electromotive force inside that coil. The greater the rate at which the change of magnetic flux happens, the higher will be the induced EMF.
This can be expressed mathematically as:
E = - dΦB / dt
Second Law (Lenz's Law): This law states that the direction of the induced current (or EMF) is always opposite to the change in magnetic flux that caused it. It is derived from the principle of conservation of energy.
This law can be mathematically represented by the negative sign appearing in Faraday's law to mean that the induced EMF opposes the change in flux.
The amount of the total magnetic field that passes through a given area is known as the magnetic flux. It describes the number of magnetic field lines passing through that area.
The mathematical formula for magnetic flux is as follows:
ΦB = B. A. cosθ
In this formula:
SI Unit: The SI unit for magnetic flux is the Weber (Wb). One Weber is defined as the amount of flux that, when passed through a coil, induces an electromotive force (EMF) of one volt if the flux is decreased to zero in one second.
Whenever a conductor moves at a velocity v perpendicular to the magnetic field B, an electromotive force, EMF, is induced in the conductor. This is an application of electromagnetic induction, where the motion of the conductor results in a change in magnetic flux.
The induced EMF can be represented by the formula:
E = B. l. v
Where:
So according to the given equation, this indicates that the induced EMF is directly proportional to the intensity of the magnetic field, the length of the conductor and the speed with which the conductor is moving.
Any device that modifies the voltage in an AC circuit is called a transformer. The electromagnetic induction principle underlies its operation. A fluctuating magnetic field is created whenever an alternating current passes through the primary coil. A voltage is subsequently induced in the secondary coil by this magnetic field. The number of turns in each coil can be used to change the secondary coil's voltage.
Working Principle: Faraday's Law of Induction serves as the foundation for how a transformer operates. It asserts that an EMF is produced in the secondary coil by fluctuating magnetic flux. The ratio of the primary coil's turns to the secondary coil's turns determines the induced EMF in the following direct manner:
Vs / Vp = Ns / Np
Where:
Self-induction occurs when an EMF, or electromotive force, is produced inside a coil by the fluctuating current. This happens as a result of a fluctuating magnetic flux created by the current itself.
The self-inductance expression is:
The EMF that self-induction causes in a coil can be calculated using:
ε = - L (dI / dt)
where:
A coil's self-induction L is affected by its physical attributes, including its area, number of turns, and core material permeability.
Lenz's Law states that the induced current, or EMF, will always flow in the opposite direction of the magnetic flux shift that generated it. The rule of conservation of energy is to blame for this.
Think of a coil in a magnetic field, for instance. An EMF is created in the coil, which results in a current if the magnetic flux through the coil is changing (for instance, when a magnet is approaching a coil). Lenz's Law states that the induced current flows in a way that causes its magnetic field to oppose the magnet's motion, or attempt to repel it.
Mutual inductance arises when two coils are placed in such a manner that the changing magnetic flux in one coil causes an electromotive force (EMF) in the other coil. The coils' mutual inductance measures the EMF produced in one coil due to the changing current in the other coil.
Expression for Mutual Inductance:
The EMF induced in the secondary coil (E_2) due to a current flowing through the primary coil (I_1) can be given by the following equation:
M= μ0N1N2A/l
Electromagnetic induction is a very important concept in physics and is used to generate electrical power, transformers, electric motors, etc. It can help the students learn and understand important concepts like Faraday's laws, Lenz's law, self and mutual inductance, and transformer action. With this, students can gain an appropriate understanding of the subject. All these will increase their chances of scoring good marks in the Class 12 exam.
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