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: 8
Grade code: 2.3.2.LI.2
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.2
Indicator code: 2.3.2.LI.2
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 turning effect (torque) experienced by a current-carrying coil in a magnetic field. This is not just an abstract concept; it is the fundamental principle behind almost every electric motor. Think about the ceiling fan cooling you down, the blender your mother uses to prepare fufu or palm nut soup, or the starter motor that brings a tro-tro's engine to life. All these devices work because of the principle we are about to learn. By understanding this, you will see how electricity and magnetism work together to create motion, a cornerstone of our modern technological world.
A. Recap: Force on a Single Current-Carrying Wire (The Motor Effect)
Before we look at a coil, let's remember the force on a single straight wire. When a wire carrying an electric current (`I`) is placed in a magnetic field (`B`), it experiences a force (`F`). The magnitude of this force is given by the formula: `F = B I L sinθ`, where `L` is the length of the wire in the field and `θ` is the angle between the wire and the magnetic field lines. The direction of this force can be found using Fleming's Left-Hand Rule. Thumb = Direction of Thrust (Force) Forefinger = Direction of the magnetic Field (North to South) Centre finger = Direction of the Current (Conventional current, + to -) B. From a Single Wire to a Rectangular Coil
Now, imagine we bend this wire into a rectangle and place it in a magnetic field, as shown below. Let's label the corners P, Q, R, and S. The current flows from P to Q, then Q to R, then R to S, and finally S back to P. The magnetic field goes from the North pole to the South pole (left to right).
*(Teacher's Note: Draw this on the board for the students to see clearly.)*