Lesson Notes By Weeks and Term v4 - SHS 3
APPLICATIONS OF ELECTRONICS
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APPLICATIONS OF ELECTRONICS
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 15
Grade code: 3.3.4.LI.3
Strand code: 3
Sub-strand code: 4
Content standard code: 3.3.4.CS.1
Indicator code: 3.3.4.LI.3
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: APPLICATIONS OF ELECTRONICS
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This lesson explores a crucial step in converting the alternating current (AC) from our wall sockets (like those provided by ECG/NEDCo) into the steady direct current (DC) that most of our electronic gadgets need to function. We use our phones, laptops, radios, and TVs every day. Have you ever wondered how the charger "brick" turns the powerful AC from the wall into the gentle DC your phone battery needs? After rectification, the DC is still "bumpy" or "pulsating". Today, we will learn how to design a simple but powerful circuit, called a smoother or filter, using a capacitor to "smooth out" these bumps and create a much more stable DC voltage.
2.1 The Problem: Pulsating DC
From our previous lessons, we know that a rectifier converts AC into DC. However, the output is not a perfectly flat, steady DC voltage like you get from a battery. A half-wave rectifier gives pulses of DC, with gaps in between. A full-wave rectifier (either centre-tapped or bridge) is better, giving a continuous series of pulses, but the voltage still drops to zero repeatedly.
This "bumpy" or pulsating DC is not suitable for most electronic devices. Imagine your phone trying to charge with a voltage that is constantly rising and falling 100 times every second! It would not work properly and could even be damaged.
*Fig 1: Output from Half-wave and Full-wave Rectifiers*