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: 7
Grade code: 2.3.2.LI.3
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.1
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 fundamental principles in physics: the motor effect. This is the magic that happens when electricity and magnetism meet. We will discover that when an electric current flows through a wire placed in a magnetic field, the wire experiences a force. This principle is not just a theory in a book; it is the force that powers countless devices we use every day in Ghana, from the fan that cools us down, to the blender in the kitchen, to the starter motor that brings a trotro or taxi to life. By understanding this concept, we unlock the secret behind how electricity is converted into useful motion.
A. The Motor Effect
The motor effect is the name given to the force experienced by a current-carrying conductor when it is placed in an external magnetic field. Key Idea: Imagine two magnets interacting. They either push each other apart (repel) or pull each other together (attract). A wire carrying an electric current creates its own magnetic field around it. When you place this wire into the magnetic field of another magnet (like a horseshoe magnet), the two magnetic fields interact. This interaction results in a physical force—a push or a pull—on the wire. Condition: This force is only produced if the conductor is not parallel to the magnetic field lines. The force is strongest when the conductor is at a right angle (90°) to the field lines.
*In the diagram, the current-carrying wire placed between the North and South poles will experience a force causing it to move either upwards or downwards.* B. Fleming's Left-Hand Rule
How do we know which way the wire will move? We use a simple but powerful tool called Fleming's Left-Hand Rule. This rule helps us determine the direction of the force (or motion). Procedure: Hold your left hand with your thumb, forefinger (index finger), and centre finger pointing at right angles (90°) to each other. Each finger represents a different quantity: ThuMb represents the direction of the Thrust or Force (the Motion). Forefinger represents the direction of the magnetic Field (from North pole to South pole). Centre finger represents the direction of the Current (conventional current, from + to -). Mnemonic (Easy way to remember): Think "Father, Mother, Child" Father -> Force (Thumb) Mother -> Magnetic Field (Forefinger) Child -> Current (Centre finger) Inclusivity Note (GESI): This is called the "Left-Hand Rule" by convention. The physics works the same for everyone, regardless of whether you are left-handed or right-handed. We all use our left hand for this specific rule to get a consistent answer. Let's practice this together as a team! C. Force Between Two Parallel Current-Carrying Conductors