Electromagnetic induction is a fundamental principle in physics that explains how a changing magnetic field can induce an electromotive force (EMF) or voltage in a conductor. This phenomenon was first discovered by Michael Faraday in the 19th century and forms the basis for the operation of many electrical devices, including generators, transformers, and even some sensors.
There are two main types of electromagnetic induction: statically induced EMF and dynamically induced EMF. Let's focus on dynamically induced EMF.
Dynamically Induced EMF:
Dynamically induced EMF refers to the creation of an electromotive force (voltage) in a conductor due to a changing magnetic field that penetrates the area enclosed by the conductor. This occurs when either the magnetic field or the conductor (or both) are in motion relative to each other. The key principle behind dynamically induced EMF is Faraday's law of electromagnetic induction.
Faraday's Law states that the magnitude of the induced EMF in a closed loop of wire is directly proportional to the rate of change of the magnetic flux through the loop. Mathematically, it can be expressed as:
=
−
Φ
E=−
dt
dΦ
Where:
E is the induced EMF in volts (V).
Φ
dt
dΦ
represents the rate of change of magnetic flux through the loop with respect to time.
Magnetic flux (
Φ
Φ) is the product of the magnetic field (
B) perpendicular to the loop, the area (
A) of the loop through which the magnetic field lines pass, and the cosine of the angle (
θ) between the magnetic field and the normal to the loop:
Φ
=
⋅
⋅
cos
(
)
Φ=B⋅A⋅cos(θ)
When the magnetic field or the loop (or both) are moving, causing the magnetic flux to change, an EMF is induced in the loop according to Faraday's law.
Applications of dynamically induced EMF include:
Generators: Electric generators use the principle of dynamically induced EMF to convert mechanical energy (from turbines, engines, etc.) into electrical energy. As the coil within the generator rotates in a magnetic field, the changing magnetic flux induces an EMF in the coil, leading to the generation of electricity.
Induction Cooktops: Induction cooktops use electromagnetic induction to directly heat pots and pans. An alternating current passing through a coil generates a changing magnetic field that induces eddy currents in the cookware, leading to heating.
Eddy Current Brakes: Some braking systems in trains and roller coasters use eddy currents (induced by the changing magnetic field) to provide controlled braking without friction.
In summary, dynamically induced EMF is a crucial phenomenon in electromagnetism, enabling the generation of electricity, wireless charging, and various other technological applications.