Contextualization

Physics plays a critical role in shaping the world around us. It helps us understand the functioning of natural and technological phenomena. One of these phenomena is linear expansion, a concept derived from the study of the thermal behavior of materials.

Linear expansion is the property of bodies to change their dimensions when subjected to temperature variations. This occurs due to the agitation of the molecules that make up the material. When the temperature increases, the agitation of these molecules also increases, causing the object to expand.

This expansion occurs in all directions, however, in linear expansion, we are only interested in the variation of the object's length. To calculate linear expansion, the formula is used:

ΔL = Lo * α * ΔT

Where:

• ΔL is the variation in the length of the object;
• Lo is the initial length of the object;
• α is the linear expansion coefficient of the material of the object;
• ΔT is the temperature variation.

Have you ever wondered why there are gaps between train tracks or why bridges have those moving parts? Linear expansion is the reason behind this. Due to temperature variations during the day and night, engineers must take into account the expansion and contraction of the materials used in the construction of structures such as bridges, train tracks, and buildings.

This concept is also used in the manufacture of mercury thermometers, where mercury expands or contracts based on the temperature and, in this way, provides us with an accurate reading. Therefore, understanding linear expansion is essential for practical application in various areas of engineering and science.

Here are some reliable sources to consolidate your knowledge of linear expansion:

• FGV - Linear Expansion
• Prof. Sérgio Pires - Linear Expansion
• UFRGS - Linear Expansion Coefficient
• Brasil Escola - Linear Expansion

Practical Activity: Exploring Linear Expansion

Project Objective

The main objective of this project is to allow students to observe and understand linear expansion through the performance of practical experiments. Students will develop skills to calculate linear expansion and understand its real-world application. In addition, this project will foster collaboration skills, time management, creative thinking, and communication.

Project Description

Students, in groups of 3 to 5, will conduct an experiment to observe the linear expansion of a metal bar when heated, and another bar of the same metal when kept at room temperature. Based on the results of the experiment, they will explore the theory of linear expansion and its applications, discussing the results and preparing a detailed report.

Required Materials

• Two identical metal bars (aluminum, copper, iron, etc.);
• Heat source (infrared lamp, for example);
• Thermometer;
• Measuring tape or metal ruler;
• Thermal gloves for handling the heated metal bars.

Step-by-Step for Activity Execution

1. Measure the initial length of the two metal bars and record the values.
2. Heat one of the bars with the heat source, keeping the other at room temperature.
3. Every 5 minutes, measure and record the temperature of the heated bar and the length of both bars.
4. Continue this process until the temperature of the heated bar stabilizes.
5. Using the formula for linear expansion, calculate the expansion coefficient of the metal.

NOTE: Safety is paramount during the execution of this project. Students should be supervised throughout the experiment. Be sure to use thermal gloves when handling the heated metal bars.

Project Delivery

Upon completing the practical part of the project, students must compose a detailed report, discussing the experiment, the results obtained, and the applications of linear expansion. The report should contain the following parts:

Introduction

Students should present the theory of linear expansion, its importance, and real-world applications. They should also describe the objective and relevance of this project.

Development

Students should discuss the methodology of the experiment, explaining each step in detail. Eg: How were the measurements taken? What safety precautions were taken? They should also present the results obtained and compare them with the theoretical ones, discussing any differences and possible reasons for these differences.

Conclusions

Students should conclude the work by summarizing their main points, explaining the learnings obtained, and drawing conclusions about linear expansion according to the experiment conducted.

Bibliography

Students should indicate the sources they relied on to work on the project such as books, web pages, videos, etc. Sources should be correctly cited according to the appropriate format.

The report must be submitted within 30 days from the start of the project. It is expected that each student contributes to the preparation of the report and the execution of the experiment, promoting effective collaboration among group members.