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: 6
Grade code: 2.3.2.LI.2
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.1
Indicator code: 2.3.2.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROMAGNETISM
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This lesson explores the fascinating interaction between electricity and magnetism, a phenomenon known as the motor effect. We will discover that when an electric current flows through a wire placed in a magnetic field, the wire experiences a force. This simple principle is the powerhouse behind countless devices we use every day in Ghana, from the fan that cools our classrooms and homes, to the blender used to prepare `shito`, and even the starter motor that cranks the engine of a `trotro` or the family car. Understanding this force is fundamental to understanding how much of our modern technology works.
A. The Motor Effect: The Fundamental Idea We know that a magnet creates a magnetic field around it. We also know from previous lessons (the work of Oersted) that an electric current flowing through a wire also creates its own circular magnetic field around the wire.
The Motor Effect is what happens when you place a current-carrying wire into an external magnetic field (e.g., between the poles of a horseshoe magnet). The two magnetic fields—the one from the magnet and the one from the current—interact with each other. This interaction produces a resultant force that pushes or pulls the wire.
Think of it like two people trying to walk through the same narrow doorway at the same time; they will push on each other. Similarly, the interacting magnetic fields "push" on the wire, causing it to move. This force is called the magnetic force or Lorentz force. B. Determining the Direction of the Force: Fleming's Left-Hand Rule
The direction of the force is not random. It can be precisely predicted using Fleming's Left-Hand Rule. How to use it: Hold up your left hand and point your first three fingers (thumb, forefinger, and middle finger) so they are all at right angles (90°) to each other. Forefinger points in the direction of the magnetic Field (from North pole to South pole). Centre (middle) finger points in the direction of the Current (conventional current, from + to -). Thumb points in the direction of the Thrust or Force (the direction the wire will move).