Linear Thermal Expansion Normal Solids Ex Glass jar

Linear Thermal Expansion

Normal Solids • • Ex. Glass jar too tight, hot water over lid. L – length T – temp. Length and temp. is directly proportional.

Thermal Expansion • Linear expansion – increase in any one dimension of a solid, linear is the expansion occurring along a line. • Change in length is proportional to both (initial) L and change in Temp. • Proportionality constant α(alpha), is called the coefficient of linear expansion.

Thermal Expansion • Coefficient of linear expansion ___ has the unit of _____. • Value of the ____ depends on the nature of the material.

Coefficients of Thermal Expansion for Solids and Liquids

Expansion Joint

Usefulness • Anti-scalding device: shuts off the flow of water when it becomes too hot, • Higher temp expands the actuator spring and pushes the plunger forward, shutting off the flow.

Homework Problem 5. If a 42 m steel footbridge experiences extreme temperatures between -12°C and 40°C, what is the range in size of this bridge if it measures exactly 42 m at 22°C? (Steel has a coefficient of linear expansion of 1. 1 x 10 -5/°C)

Calculate Length for each set of values • L 1=L(1+α∆T 1) T 1= -12 -22=-34 42(1+ 1. 1 x 10 -5(-34))=41. 9843 m L 2=L(1+ α∆T 2) T 2=40 -22=18 42(1+ 1. 1 x 10 -5 (18))=42. 0083 ∆L=L 2 -L 1 42. 0083 -41. 9843=. 024024 m