Lesson Notes By Weeks and Term v4 - SHS 2
ELECTROSTATICS
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ELECTROSTATICS
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Subject: Physics
Class: SHS 2
Term: 2nd Term
Week: 1
Grade code: 2.3.1.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 2.3.1.CS.1
Indicator code: 2.3.1.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROSTATICS
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Have you ever felt a small shock when you touched a metal doorknob after walking on a carpet, especially during the dry Harmattan season? Or seen a balloon stick to a wall after rubbing it on your hair? These are everyday examples of electrostatics – the study of stationary electric charges. While these small effects seem like magic, they are governed by a fundamental law of physics. This lesson introduces Coulomb's Law, which allows us to precisely measure the force that these charges exert on each other. Understanding this law is the first step to understanding everything from lightning to how a photocopier works.
a. Electric Charge and Point Charges Electric Charge (q): A fundamental property of matter. It can be positive (+) or negative (-). Protons carry a positive charge, and electrons carry a negative charge. Unit of Charge: The SI unit for electric charge is the Coulomb (C). One Coulomb is a very large amount of charge, so we often work with smaller units like the microcoulomb (μC, 1μC = 10⁻⁶ C) or the nanocoulomb (nC, 1nC = 10⁻⁹ C). Point Charge: An idealized charged object whose size is negligible compared to the distance between it and other charged objects. We use this concept to simplify our calculations. b. The Nature of the Electrostatic Force: Attraction and Repulsion The core principle of electrostatic interaction is simple: Like charges repel: Two positive charges will push each other away. Two negative charges will also push each other away. Unlike charges attract: A positive charge and a negative charge will pull towards each other.
This direction of the force is crucial. When solving problems, we first determine if the force is attractive or repulsive, and then we calculate its strength (magnitude). c. Coulomb's Law Charles-Augustin de Coulomb discovered the mathematical relationship that describes this force.
In Words: > Coulomb's Law states that the electrostatic force between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them.
Let's break this down: "Directly proportional to the product of the magnitudes of the charges" means if you double one charge, the force doubles. If you double both charges, the force becomes four times stronger (2 x 2 = 4). "Inversely proportional to the square of the distance" means the force weakens rapidly as the charges move apart. If you double the distance, the force becomes four times weaker (1/2² = 1/4). If you triple the distance, the force becomes nine times weaker (1/3² = 1/9). This is known as an inverse-square law.