Lesson Notes By Weeks and Term v4 - SHS 3
ELECTROMAGNETIC INDUCTION & APPLICATIONS
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ELECTROMAGNETIC INDUCTION & APPLICATIONS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 9
Grade code: 3.3.3.LI.2
Strand code: 3
Sub-strand code: 3
Content standard code: 3.3.3.CS.2
Indicator code: 3.3.3.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROMAGNETIC INDUCTION & APPLICATIONS
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Good day, students. Today, we are going to explore one of the most important principles in all of physics: Electromagnetic Induction. This is the magic behind how we generate almost all the electricity we use in Ghana, from the giant turbines at the Akosombo Dam to the small petrol generator your family might use during a power outage ("dumsor"). It’s also the principle that makes a simple bicycle lamp light up without a battery. By understanding this topic, you will understand the heart of our modern electrical world.
2.1. The Foundation: Faraday's and Lenz's Laws
The entire topic rests on one simple idea: a changing magnetic field can create an electric current.
A. Magnetic Flux (Φ) Think of magnetic flux as the total number of magnetic field lines passing through a given area (like a coil of wire). Formula: Φ = BAcos(θ) Where: Φ is the magnetic flux (measured in Weber, Wb) B is the magnetic field strength (Tesla, T) A is the area of the coil (m²) θ is the angle between the magnetic field lines and the normal (perpendicular) to the area. *Maximum flux* occurs when the field lines are perpendicular to the coil's surface (θ = 0°, cos(0°)=1). *Zero flux* occurs when the field lines are parallel to the coil's surface (θ = 90°, cos(90°)=0).
B. Faraday's Law of Electromagnetic Induction This law gives us the "how much." It states that the magnitude of the induced electromotive force (e.m.f. or ε) in a coil is directly proportional to the rate of change of magnetic flux linkage. Formula: ε = -N (ΔΦ / Δt) Where: ε is the induced e.m.f. (Volts, V) N is the number of turns in the coil. ΔΦ is the change in magnetic flux (Wb). Δt is the time taken for the change (s). The term (ΔΦ / Δt) is the *rate of change of magnetic flux*.