Lesson Notes By Weeks and Term v4 - SHS 3
DIRECT CURRENT
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
DIRECT CURRENT
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 4
Grade code: 3.3.1.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 3.3.1.CS.3
Indicator code: 3.3.1.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: DIRECT CURRENT
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Welcome, future engineers and scientists! In our homes and communities, we rarely deal with simple, single-loop electrical circuits. From the complex wiring in our houses that allows us to use a fan, a television, and charge our phones all at once, to the Electricity Company of Ghana (ECG) distributing power to different neighbourhoods, electricity is constantly being divided and managed. This lesson focuses on the fundamental principles that govern how voltage and current are shared in different parts of a circuit.
A. Recap: Foundational Knowledge
Before we introduce dividers, let's remember two key principles you learned in SHS1 and SHS2: Ohm's Law: The voltage (V) across a resistor is directly proportional to the current (I) flowing through it, provided the physical conditions remain constant. `V = IR` Resistors in Series: The total equivalent resistance (`R_T`) is the sum of individual resistances. The current is the same through all resistors. `R_T = R₁ + R₂ + ... + Rₙ` Resistors in Parallel: The reciprocal of the total equivalent resistance (`R_T`) is the sum of the reciprocals of individual resistances. The voltage is the same across all branches. `1/R_T = 1/R₁ + 1/R₂ + ... + 1/Rₙ` For two resistors, a useful shortcut is: `R_T = (R₁ * R₂) / (R₁ + R₂)` B. The Voltage Divider Principle
Concept: Imagine you have a 12V car battery and you need to power a small electronic component that requires only 4V. You cannot connect it directly! A voltage divider is a simple circuit that turns a large voltage into a smaller one.
In any series circuit, the total source voltage is shared or *divided* among all the resistors. The portion of voltage each resistor gets is proportional to its resistance. A larger resistor gets a larger share of the voltage.