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: 16
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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In Ghana, nearly every home and business uses electronic devices that plug into the wall sockets provided by the Electricity Company of Ghana (ECG). These sockets supply Alternating Current (AC), but our most common gadgets—like mobile phones, laptops, and radios—need steady Direct Current (DC) to function. The process of converting AC to DC is called rectification. However, the DC from a simple rectifier is not smooth; it's a pulsating, bumpy voltage. This bumpy DC can damage sensitive electronics. Today's lesson focuses on the crucial next step: smoothing or filtering.
This lesson builds on our previous knowledge of AC, DC, and rectification. Let's start with a quick recap. 2.1. The Problem: Pulsating DC from a Rectifier
The power from our wall sockets is AC (Alternating Current). The voltage repeatedly swings from positive to negative.
A rectifier circuit (using diodes) converts this AC into DC by blocking or redirecting the negative half of the cycle. However, the output is not a steady, flat line of voltage. It is pulsating DC. Half-Wave Rectifier: Chops off the negative half, leaving gaps. Full-Wave Rectifier: Flips the negative half to become positive, filling the gaps but still creating pulses.
This pulsating DC is unsuitable for most electronic devices. Imagine trying to power your phone with a voltage that continuously drops to zero! It would not work correctly. We need to smooth out these "hills" and "valleys". 2.2. The Solution: The Capacitor as a Filter