Lesson Notes By Weeks and Term v4 - SHS 2

Lesson Video

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Performance objectives

• Define what a capacitor is.
• Identify and describe different types of capacitors.
• Explain the main functions of a capacitor in a circuit.
• Calculate the value of a capacitor using its color code.

Lesson summary

Welcome, learners. Today, we are exploring a tiny but powerful component that makes most of our modern electronic gadgets work: the capacitor. Think about your mobile phone, the fan in the classroom, the radio you listen to, or even the flash on a camera. All these devices rely on capacitors to function correctly. In Ghana, where our power supply from ECG can sometimes be unstable, capacitors play a vital role in protecting our devices by smoothing out power fluctuations. Understanding how they work is a fundamental step in learning how to repair and build electronic circuits, opening up opportunities in electronics repair, engineering, and technology innovation.

Lesson notes

A. What is a Capacitor?

A capacitor is a component that stores electrical energy in an electric field. Analogy: Think of a capacitor like a small, very fast water tank (`tanki`). You can fill the tank with water (charge) and then open the tap to release all the water very quickly. Similarly, a capacitor can be charged with electricity and then discharge it rapidly when needed. Structure: A simple capacitor is made of two metal plates (conductors) placed very close to each other but not touching. They are separated by an insulating material called a dielectric. The dielectric can be made of paper, ceramic, plastic, or even air.

``` Terminal 1 ---[ Plate 1 ] | Dielectric | <-- The insulating material Terminal 2 ---[ Plate 2 ] ``` Capacitance: This is the measure of a capacitor's ability to store charge. The unit of capacitance is the Farad (F), named after Michael Faraday. One Farad is a very large unit. In electronics, we commonly use smaller units: Microfarad (µF): One millionth of a Farad (10⁻⁶ F) Nanofarad (nF): One billionth of a Farad (10⁻⁹ F) Picofarad (pF): One trillionth of a Farad (10⁻¹² F) Conversions: 1 µF = 1,000 nF 1 nF = 1,000 pF 1 µF = 1,000,000 pF B. Types of Capacitors

There are many types, but we will focus on two very common ones. Electrolytic Capacitors Appearance: They look like small cylindrical cans, usually black, blue, or brown. They have two legs (leads) of different lengths. Key Feature (Polarity): They are polarised. This means they have a positive (+) terminal and a negative (-) terminal. The negative terminal is clearly marked with a stripe and minus signs (-) on the body of the capacitor. The longer leg is the positive terminal. Important: You MUST connect an electrolytic capacitor the correct way in a circuit. Connecting it backwards can cause it to heat up, leak, and even explode! Capacitance: They offer high capacitance values (e.g., 1µF to over 10,000µF). Common Use: Power supply filtering (smoothing DC voltage), audio coupling. You will find them in phone chargers, radios, and amplifiers. Ceramic Capacitors Appearance: They are small, disc-shaped (like a small, flat button), and often brown or orange in colour. Key Feature (Non-Polarised): They are non-polarised. You can connect them in a circuit in either direction without damaging them. Capacitance: They have small capacitance values (usually in the picofarad or nanofarad range). Markings: Their values are often written on them using a number code (e.g., "104") or a colour code, which we will learn to calculate. Common Use: High-frequency circuits, filtering out noise, and timing circuits. They are found everywhere on circuit boards. C. Functions of a Capacitor

Evaluation guide

• Describe types capacitor as a passive electronic component
• Collaborative Learning: Using videos and pictures engage learners in mixed ability
• groups to undergo the following activities:
• Define capacitor