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: 11
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 one of the most important principles in physics: the motor effect. This is the principle that allows us to convert electrical energy into useful mechanical motion. We see this magic happen all around us in Ghana. When you switch on a fan to cool down, use a blender to prepare palm nut soup, or see a corn mill grinding maize, you are witnessing the power of the electric motor. We will investigate the structure and working principle of the DC electric motor and a very sensitive measuring instrument that uses the same principle, the moving coil galvanometer. Understanding these devices is fundamental to understanding much of the technology that powers our modern world.
A. The Foundation: The Motor Effect
The entire operation of electric motors and moving coil galvanometers is based on a single, fundamental principle: 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.
This force (often called the Lorentz force or motor force) depends on three things: The strength of the magnetic field (B), measured in Tesla (T). The magnitude of the electric current (I), measured in Amperes (A). The length of the conductor inside the magnetic field (L), measured in metres (m). The angle (θ) between the conductor and the magnetic field lines.