CHAPTER 15: ELECTROMAGNETIC INDUCTION

How does a generator produce electricity? How does a transformer change voltage? How do induction cooktops heat food without flame? The answer lies in electromagnetic induction—the process by which a changing magnetic field creates an electric current. Discovered by Michael Faraday in 1831, this principle is the foundation of almost all electrical power generation and distribution in the world. This chapter will give you mastery over Faraday's Law, Lenz's Law, generators, and transformers.

15.1 MAGNETIC FLUX AND FLUX LINKAGE

Before understanding induction, we must understand the concept of magnetic flux.

15.1.1 Magnetic Flux (Φ)

Magnetic flux is a measure of the total magnetic field passing through a given area. It depends on the magnetic field strength, the area, and the angle between the field and the area.

Φ = B × A × cosθ

Where:

• Φ = magnetic flux (weber, Wb)
• B = magnetic flux density (tesla, T)
• A = area through which the field passes (m²)
• θ = angle between the magnetic field direction and the normal (perpendicular) to the area

When the field is perpendicular to the area (θ = 0°), cosθ = 1, and Φ = B × A.

15.1.2 Magnetic Flux Linkage

For a coil of N turns, the flux linkage is the total flux passing through all turns:

Flux linkage = N × Φ = N B A cosθ

Flux linkage is measured in weber-turns (Wb-turns) or simply webers.

Worked Example (Flux Calculation):

A rectangula