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: 13
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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Today, we delve into a fascinating consequence of electromagnetic induction known as Eddy Currents. While they can sometimes be a source of unwanted energy loss in devices like transformers, engineers have cleverly harnessed their power for incredible applications. We will see how these 'whirlpools' of current can melt metal without fire, stop a fast-moving train without touching it, and help us get accurate readings from our lab instruments. Understanding eddy currents is crucial for appreciating the design of many electrical devices we use daily, from the electricity meter outside our homes to the systems that keep modern transport safe.
2.1. What are Eddy Currents? (Recalling Faraday's and Lenz's Laws)
We already know Faraday's Law of Electromagnetic Induction: When the magnetic flux linkage with a conductor changes, an electromotive force (e.m.f.) is induced in it. If the conductor is a closed circuit, this e.m.f. drives a current.
Now, consider what happens when the conductor is not a thin wire, but a solid block or plate of metal (a bulk conductor).
If we change the magnetic flux through this metal plate, an e.m.f. is induced. Since the metal plate is a conductor, this e.m.f. will drive currents. These induced currents do not have a single path to follow like in a wire. Instead, they flow in closed loops within the body of the conductor, resembling eddies or whirlpools in water.