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: 18
Grade code: 1.3.3.LI.3
Strand code: 3
Sub-strand code: 3
Content standard code: 1.3.3.CS.2
Indicator code: 1.3.3.LI.3
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: ANALOGUE ELECTRONICS
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This lesson introduces the fascinating world of transducers – special electronic components that act as bridges between the physical world and the world of electricity. In our daily lives in Ghana, we are surrounded by these devices. From the microphone a preacher uses in church, to the loudspeaker at a community information centre, the motor in a rechargeable fan during 'dumsor', and the remote control for our television, transducers are everywhere. Understanding how they work is fundamental to understanding modern technology.
A. What is a Transducer?
A transducer is any device that converts energy from one form to another. In electronics, we are usually interested in devices that convert between electrical energy and some other form of energy (like sound, light, pressure, or motion). Input Transducers (Sensors): They detect a physical quantity and convert it into an electrical signal. Example: A microphone detects sound and turns it into an electrical signal. Output Transducers (Actuators): They take an electrical signal and convert it into a physical output. Example: A loudspeaker takes an electrical signal and turns it into sound.
Think of it like translating a language. A microphone "translates" the language of sound into the language of electricity. A loudspeaker "translates" it back.
B. How Transducers Work (The Processes) The Microphone (Dynamic Type) Function: Converts sound energy (mechanical wave) into electrical energy (audio signal). Key Principle: Electromagnetic Induction (A changing magnetic field through a coil of wire induces a voltage). Process: Sound Waves Arrive: When someone speaks or sings, sound waves (which are vibrations in the air) travel and hit a thin, flexible sheet inside the microphone called a diaphragm. Diaphragm Vibrates: The diaphragm vibrates back and forth, exactly matching the pattern of the sound waves (high-pitch sounds cause fast vibrations, loud sounds cause large vibrations). Coil Moves: Attached to the back of the diaphragm is a small coil of wire, known as the voice coil. This coil is placed in a magnetic field created by a permanent magnet. As the diaphragm vibrates, the coil also moves back and forth within this magnetic field. Voltage is Induced: According to the principle of electromagnetic induction, whenever a conductor (the coil) moves through a magnetic field, a voltage is induced across its ends. The movement of the coil "cuts" the magnetic field lines. Signal is Created: The induced voltage changes in exact proportion to the vibration of the coil. This changing electrical voltage is the audio signal. It is a faithful electrical copy of the original sound wave.