Lesson Notes By Weeks and Term v4 - SHS 2
ELECTROMAGNETISM
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ELECTROMAGNETISM
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Subject: Physics
Class: SHS 2
Term: 2nd Term
Week: 12
Grade code: 2.3.2.LI.4
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.2
Indicator code: 2.3.2.LI.4
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROMAGNETISM
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Welcome, students! Today, we are exploring a fascinating and highly practical application of electromagnetism: the electromagnetic switch, more commonly known as a relay. Think about this: to start a car, you turn a small key. But that small action makes a very powerful engine roar to life. How can such a small current from the key control the huge current needed by the starter motor? The secret lies in the relay.
A. The Foundation: The Electromagnet
Before we can understand the switch, we must remember what an electromagnet is. Definition: An electromagnet is a temporary magnet made by passing an electric current through a coil of wire (a solenoid) that is wrapped around a soft iron core. Principle: When current flows, a magnetic field is created. The soft iron core concentrates this magnetic field, making it much stronger. Key Property: The magnetism can be switched on and off instantly. Current ON -> Magnetism ON Current OFF -> Magnetism OFF
This "on/off" ability is the heart of the electromagnetic switch. B. The Electromagnetic Switch (The Relay)
A relay is an electrically operated switch. Its main purpose is to use a small current in one circuit to switch a much larger current in another circuit, without the two circuits being electrically connected. C. Construction of a Relay