# Faradays Law of Induction Explained

#### By R.W. Hurst, The Electricity Forum

Faradays Law of Induction, formulated by Michael Faraday, is a fundamental principle in electromagnetism. It describes how a changing magnetic field within a closed loop induces an electromotive force (EMF) in the conductor. This phenomenon, known as electromagnetic induction, is the basis for many electrical devices and technologies, such as transformers, electric motors, and generators.

What is Faradays Law of Induction?

At its core, Faraday's Law states that a changing magnetic field induces an electromotive force (EMF) within a loop of wire. This EMF, often regarded as voltage, drives an electric current if the circuit is closed.  The magnitude of the induced EMF is proportional to the rate of change of the magnetic flux through the loop.

Mathematically, Faraday's Law is expressed as:

EMF=−NΔtΔΦ​

where:

EMF is the induced electromotive force (voltage)
N is the number of turns in the coil
ΔΦ is the change in magnetic flux
Δt is the change in time

Why is EMF regarded as voltage?

EMF is regarded as voltage because it represents the potential difference that drives the electric current through a circuit. Essentially, EMF is the voltage generated by a change in the magnetic environment of the circuit.

How is the EMF induced, and why?

EMF is induced when there is a change in the magnetic flux through a loop of wire. This change can occur by moving a bar magnet towards or away from the coil, altering the field strength, or changing the area of the coil exposed to the magnetic field. Faraday's Law quantifies this induction, stating that the induced EMF is proportional to the rate of change of the magnetic flux. The negative sign in the equation indicates that the induced EMF acts to oppose the change in flux, a principle known as Lenz's Law.

Why does an induced EMF induce a current in the coil?

An induced EMF induces a current in the coil due to Ohm's Law, which states that 𝑉=𝐼𝑅V=IR (voltage equals current times resistance). When an EMF is induced, it creates a potential difference that causes current to flow through the coil if the circuit is closed. Even in the absence of an initial current, the induced voltage (EMF) drives the current through the coil​.

Why is the magnetic field strength experienced by the coil increased when a bar magnet approaches it?

The magnetic field strength experienced by the coil increases when a bar magnet approaches because the magnetic flux through the coil increases. As the bar magnet gets closer, the magnetic field lines become denser within the area of the coil, increasing the magnetic flux and inducing a stronger EMF.

Does Faraday's law work under the assumption that there is no current flowing through the solenoid that has been produced by a power source?

Yes, Faraday's Law applies to situations where the current is induced by changing magnetic fields rather than being supplied by an external power source. The magnetic field in a solenoid can interact with an approaching bar magnet to induce EMF without any initial current in the solenoid.

Faraday's Law of Induction is universally applicable in explaining how changing magnetic fields can induce voltage (EMF) in conductors. It is fundamental to the working principles of many electrical devices and technologies.

What is the significance?

The significance of Faraday's Law of Induction lies in its ability to explain the generation of electric currents in response to changing magnetic fields. This principle is crucial for the operation of electric generators, transformers, and inductors, making it a foundational concept in both theoretical and applied electromagnetism.

Which among the following best explains Faraday's law of induction?

Faraday's Law of Induction is best explained as the process by which a changing magnetic flux induces an electromotive force (EMF) in a closed circuit, resulting in the generation of electric current if the circuit is closed​ (Khan Academy)​​ (Sciencing)​.

How is it used in everyday life?

Faraday's Law is used in various everyday applications, such as in electric generators where mechanical energy is converted into electrical energy, in transformers that transfer electrical energy between circuits, and in induction cooktops that use electromagnetic induction to heat cookware​.

Faraday's Law, combined with Lenz's Law and Maxwell's equations (James Clerk Maxwell), provides a comprehensive framework for understanding electromagnetic phenomena, making it a critical component of modern electrical engineering and physics. The interplay between the rate of change of magnetic flux (and therefore to oppose the change in magnetic flux), the number of turns in the coils of wire, and the uniform magnetic field exemplifies the intricate relationships described by Faraday.

Faraday's Law is ubiquitous in modern technology. It is used in:

• Electric generators to convert mechanical energy into electrical energy.
• Transformers to step up or down voltages in power transmission.
• Induction cooktops to heat cookware directly through magnetic fields.
• Magnetic swipe cards for security and identification.
• Many other applications in electronics and engineering.

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