Faraday's Law of Induction: The Foundation of Electromagnetic Generation

Expert reviewed • 22 November 2024 • 5 minute read

Introduction

Faraday's Law of Induction stands as one of the fundamental principles of electromagnetism, explaining how changing magnetic fields can generate electric current. This principle forms the basis of modern electrical generators and transformers.

The Discovery of Electromagnetic Induction

In 1831, Michael Faraday made a groundbreaking discovery using a simple yet ingenious setup. [Image 1] He wrapped two separate coils of wire around an iron ring, connecting one to a battery and the other to a galvanometer. Upon closing the circuit, he observed a momentary deflection in the galvanometer, indicating the presence of an induced current.

Understanding Faraday's Law

Faraday's Law states that an electromotive force (EMF) is induced in a conductor when it experiences a change in magnetic flux. The induced EMF (ε) is given by:

ε=−NΔϕΔt\varepsilon = -N\frac{\Delta\phi}{\Delta t}

Where:

  • ε = induced EMF (volts, V)
  • N = number of turns in the coil
  • Δφ = change in magnetic flux (webers, Wb)
  • Δt = time interval (seconds, s)

Magnetic Flux

The magnetic flux (φ) through a surface is defined as:

ϕ=BAcos⁡θ\phi = BA\cos\theta

Where:

  • B = magnetic field strength (tesla, T)
  • A = area of the conductor (square meters, m²)
  • θ = angle between the magnetic field lines and the surface normal

Factors Affecting Induced EMF

Several factors influence the magnitude of induced EMF:

  • Rate of Change: Faster changes in magnetic flux produce larger EMF
  • Number of Coil Turns: More turns result in greater induced EMF
  • Magnetic Field Strength: Stronger fields lead to larger flux changes
  • Coil Area: Larger cross-sectional areas intercept more magnetic flux
  • Orientation: Maximum EMF occurs when field lines are perpendicular to the coil

Practical Applications

The principle finds extensive applications in:

  • Electric generators
  • Power transformers
  • Induction motors
  • Electromagnetic sensors
  • Wireless charging systems

Practice Question 1

Consider a coil with 10 turns experiencing a flux change from 0.50 Wb to 0 Wb over 1.5 seconds. Calculate the induced EMF.
The induced EMF is: ε=−NΔϕΔt=−(10)0−0.501.5=3.33 V\begin{align*} \varepsilon &= -N\frac{\Delta\phi}{\Delta t} \\ &= -(10)\frac{0 - 0.50}{1.5} \\ &= 3.33 \text{ V} \end{align*}

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Lenz's Law

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