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: 9
Grade code: 2.3.2.LI.3
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.2
Indicator code: 2.3.2.LI.3
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROMAGNETISM
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This lesson explores the fascinating and powerful application of the motor effect: the principle that turns electricity into motion. We see this magic happen all around us every day in Ghana – from the fan that cools us down, to the blender that prepares our soup, to the starter motor that brings a tro-tro's engine to life. We will investigate the two key devices that use this principle: the DC electric motor, which creates continuous motion, and the moving coil galvanometer, which is designed to precisely measure small electric currents. By understanding these devices, we unlock the secrets behind much of our modern technology.
A. The Foundation: The Motor Effect and Fleming's Left-Hand Rule
Before we discuss the motor and galvanometer, we must remember the core principle that makes them work: The Motor Effect. Definition: The motor effect is the phenomenon where a conductor carrying an electric current experiences a force when it is placed in a magnetic field.
The direction of this force is not random. We can predict it using Fleming's Left-Hand Rule. How to Use the Rule: Hold your left hand with your Thumb, Forefinger (index finger), and Centre finger all pointing at 90° (perpendicular) to each other. Forefinger points in the direction of the magnetic Field (from North pole to South pole). Centre finger points in the direction of the Current (conventional current, from + to -). Your Thumb will then point in the direction of the Thrust or Force on the conductor.
This rule is the key to understanding how both motors and galvanometers work.