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: 4
Grade code: 2.3.1.LI.4
Strand code: 3
Sub-strand code: 1
Content standard code: 2.3.1.CS.2
Indicator code: 2.3.1.LI.4
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ELECTROSTATICS
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This lesson focuses on the capacitor, a fundamental electronic component that stores electrical energy. While it seems like a simple device, its behaviour changes dramatically depending on the type of electrical circuit it is in. We will explore how a capacitor acts in Direct Current (DC) circuits, like those powered by batteries, and in Alternating Current (AC) circuits, like the power we get from the Electricity Company of Ghana (ECG). Understanding this is crucial because capacitors are everywhere in our daily lives in Ghana – from the chargers we use for our phones and laptops, to the ceiling fans that keep us cool, and even the radios we use when the "light goes off".
Part 1: What is a Capacitor?
A capacitor is an electronic component that stores electrical energy in an electric field. Structure: The simplest capacitor consists of two parallel conductive plates (usually metal) separated by a non-conductive material called a dielectric (e.g., air, paper, ceramic, plastic). Symbol: Non-polarised capacitor: `—| |—` Polarised capacitor (like an electrolytic one): `—| (—` (The curved plate is usually the negative terminal). Function: Think of it like a small, very fast rechargeable battery. It can be charged up with electrical energy and can then release that energy very quickly. Capacitance (C): This is the measure of a capacitor's ability to store charge. The unit of capacitance is the Farad (F). One Farad is a very large unit, so we often use microfarads (µF, 10⁻⁶ F), nanofarads (nF, 10⁻⁹ F), and picofarads (pF, 10⁻¹² F). Part 2: Behaviour of a Capacitor in a DC Circuit
A DC (Direct Current) circuit is one where the current flows in only one direction. A battery is a common DC source.
A. Charging a Capacitor