Lesson Notes By Weeks and Term v4 - SHS 3
ELECTROMAGNETIC INDUCTION & APPLICATIONS
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ELECTROMAGNETIC INDUCTION & APPLICATIONS
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 12
Grade code: 3.3.3.LI.1
Strand code: 3
Sub-strand code: 3
Content standard code: 3.3.3.CS.2
Indicator code: 3.3.3.LI.1
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROMAGNETIC INDUCTION & APPLICATIONS
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Welcome, future engineers and scientists! Today, we delve into a fascinating and practical aspect of electromagnetism called Eddy Currents. Have you ever noticed the large, grey transformers on electricity poles in your community getting warm, or heard of modern kitchens using induction cookers that heat pots without a flame? The principles behind these are rooted in eddy currents. Understanding these "swirling" currents is crucial, as they can be both a source of wasteful energy loss (like in ECG transformers) and a powerful tool for modern technology, from braking systems to industrial furnaces.
2.1. Recap: Faraday's and Lenz's Laws
Before we can understand eddy currents, let's refresh our memory on the two foundational laws: Faraday's Law of Electromagnetic Induction: States that whenever the magnetic flux linked with a conductor changes, an electromotive force (EMF) is induced in the conductor. The magnitude of this induced EMF is directly proportional to the rate of change of the magnetic flux. (ε = -N * ΔΦ/Δt). Lenz's Law: States that the direction of the induced current is such that it creates a magnetic field that opposes the very change in magnetic flux that produced it. This is the "law of opposition" and is why there is a negative sign in Faraday's equation. 2.2. What are Eddy Currents?
Imagine pouring water into a narrow pipe – it flows in a straight line. This is like current in a wire. Now, imagine stirring water in a wide basin – it swirls in circles, creating "eddies" or whirlpools.
Definition: Eddy currents (also known as Foucault currents) are loops of electrical current induced within a bulk conductor by a changing magnetic field in the conductor, according to Faraday's law of induction.