Lesson Notes By Weeks and Term v4 - SHS 1
ANALOGUE ELECTRONICS
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ANALOGUE ELECTRONICS
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Subject: Physics
Class: SHS 1
Term: 2nd Term
Week: 17
Grade code: 1.3.3.LI.1
Strand code: 3
Sub-strand code: 3
Content standard code: 1.3.3.CS.1
Indicator code: 1.3.3.LI.1
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ANALOGUE ELECTRONICS
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Welcome, students! Today, we are diving into a very practical part of physics called Analogue Electronics. Look around you – the small light on your phone that shows it's charging, the bright traffic lights in Accra or Kumasi, the screen of the television at home. Many of these use the technology we will discuss today. We will explore two key components: the Light Emitting Diode (LED) and the Zener Diode. Understanding these components is crucial because they are the building blocks of modern gadgets, helping us save energy and protecting our valuable electronics from damage.
This lesson is in two parts. First, we will look at LEDs, the components that give us light efficiently. Second, we will study Zener diodes, the components that protect our gadgets. Part A: The Light Emitting Diode (LED) What is an LED? An LED is a special type of diode. A regular diode is an electronic component that allows electric current to flow in only one direction, like a one-way street or a valve in a water pipe.
An LED does the same thing, but with a special property: when current flows through it in the correct direction (this is called forward bias), it emits light. It converts electrical energy directly into light energy. Key Idea: It's a semiconductor device. It doesn't have a filament that burns like old bulbs. Circuit Symbol: The symbol is like a regular diode's symbol (a triangle pointing towards a bar) but with two small arrows pointing away from it, indicating that it emits light.
``` Anode (+) Cathode (-) ───|>|─── ^ | (Light Emitted) ``` The Anode is the positive terminal. The Cathode is the negative terminal. Current flows from Anode to Cathode. Benefits of Using LEDs (Analysis) Why are we seeing LEDs everywhere, replacing the old, round, glass bulbs (incandescent bulbs)? Let's analyse the reasons. Benefit 1: Energy Efficiency Explanation: LEDs convert a very high percentage of electrical energy directly into light. Very little energy is wasted as heat. Incandescent bulbs, on the other hand, work by heating a tiny wire (filament) until it glows white-hot. They are more like heaters that happen to produce light, wasting over 90% of their energy as heat. Ghanaian Context: Think about your ECG prepaid or postpaid bill. A 10-watt LED bulb can produce the same amount of light as a 100-watt incandescent bulb. If you use the bulb for 5 hours, the incandescent bulb uses `100W * 5h = 500 Wh` of energy. The LED uses only `10W * 5h = 50 Wh`. You use 10 times less electricity! This saves your family money and reduces the overall load on the national power grid. Benefit 2: Long Lifespan Explanation: Because LEDs don't have a delicate filament that can burn out, they last much, much longer. Comparison: Typical Incandescent Bulb: ~1,000 - 2,000 hours Typical LED Bulb: ~25,000 - 50,000 hours Impact: This means you buy bulbs less often, saving money in the long run and creating less waste for our environment. This demonstrates adaptability to new, more sustainable technologies. Benefit 3: Durability and Robustness Explanation: LEDs are "solid-state" devices. They are made from solid material with no fragile glass parts or filaments. This makes them very resistant to shock, vibrations, and impact. Example: If you shake an old bulb, you might hear the filament rattle. If it drops, it shatters. An LED is much tougher. This is why they are perfect for use in cars, torches ('kamboo'), and traffic lights that have to endure vibrations and harsh weather. Benefit 4: Compact Size Explanation: Individual LEDs are tiny. This allows them to be used in a huge variety of devices where space is limited. Examples: The notification light on your phone, the backlight for your TV or laptop screen, indicator lights on your stabilizer or power bank.
Part B: The Zener Diode What is a Zener Diode? A Zener diode is another special type of diode. While a regular diode is designed to block current in the reverse direction, a Zener diode is specifically designed to work in reverse bias.