Lesson Notes By Weeks and Term v4 - SHS 3
DIRECT CURRENT
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DIRECT CURRENT
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 3
Grade code: 3.3.1.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 3.3.1.CS.2
Indicator code: 3.3.1.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: DIRECT CURRENT
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Good morning, class. Think about the fan in your classroom or at home. How do you change its speed? Or the volume knob on a radio – how does turning it make the sound louder or softer? These everyday devices work because of special components that can control the amount of electricity flowing through them. Unlike a normal resistor that has a fixed value (like a 10 Ω resistor), these components can *change* their resistance. Today, we will explore these fascinating devices called variable resistors, specifically the rheostat and the potentiometer.
A. What is a Variable Resistor?
A resistor is a component that opposes the flow of electric current. Most resistors you have seen so far are fixed resistors – their resistance value is constant.
A variable resistor is an electronic component whose resistance can be changed or adjusted manually. They are also known as potentiometers or rheostats.
The fundamental principle behind most variable resistors is the relationship between resistance (R), resistivity (ρ), length (L), and cross-sectional area (A) of a conductor: R = ρL / A