Lesson Notes By Weeks and Term v4 - SHS 3
HEAT
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
HEAT
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 17
Grade code: 3.2.1.LI.3
Strand code: 2
Sub-strand code: 1
Content standard code: 3.2.1.CS.1
Indicator code: 3.2.1.LI.3
Theme: ENERGY
Subtheme: HEAT
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.
This lesson explores thermal expansion, a fundamental effect of heat energy. We see its effects all around us in Ghana, from the sagging of ECG power lines on a hot afternoon to the small gaps left in bridges like the Adome Bridge or on our railway lines. Understanding why materials expand when heated and how different materials expand by different amounts is crucial for engineers, builders, and technicians to design safe and durable structures. This lesson focuses on linear (or length) expansion in metals and how we can compare them.
A. What is Thermal Expansion?
When most substances are heated, they expand. When they are cooled, they contract. This phenomenon is called thermal expansion. At the particle level: Solids are made of atoms or molecules held together in a fixed structure, vibrating about their mean positions. When heat energy is supplied, these particles gain kinetic energy and vibrate more vigorously. This increased vibration causes them to push their neighbours further apart, leading to an overall increase in the size (length, area, or volume) of the solid. B. Linear Expansion
For a solid object like a rod, wire, or railway track, the expansion in length is often the most important. Linear Thermal Expansion is the increase in the length of a solid when its temperature is increased.
The change in length ($\Delta L$) of a solid is found to be directly proportional to: The original length ($L_0$). A longer rod will expand more than a shorter one. The change in temperature ($\Delta T$). A larger temperature increase will cause a greater expansion.