Thermal Physics Physics 1X, Exercises of Thermal Physics

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Physics: Section 12.

Linear Expansion / Volumetric Expansion

 Most solids and liquids expand when heated and

contract when cooled.

 In most solids and liquids, when temperature rises,

their molecules vibrate more and have more kinetic

energy.

 At these higher levels of vibration, the particles aren’t

bound to each other as tightly, so the object expands.

Thermal Expansion

Linear Expansion Amount of linear expansion (L) depends on the following:

1. T (Tfinal – Tinitial) : Change in temperature (ºC)
2. Li : Original length
3.  (alpha) : Coefficient of thermal expansion

Units for Coefficient of Thermal Expansion  units: 1/ºC

Thermal Expansion

L =  Li T

Change In Temperature (Final – Initial)

Original Length Coefficient Of Thermal Change Expansion In Length

Linear Expansion Formula

 Alpha () is material dependent, i.e. it’s different for steel, aluminum, concrete, etc.

 Since the coefficient of linear expansion is different for different materials, therefore each substance has its own rate of expansion.

 Reference Sheet

Linear Expansion - FYI

A Brass strip is 3 cm long at 0ºC. How long will it be at 100ºC if the coefficient of linear expansion for Brass is 1.8 x 10-5/ºC?

Δ L = ()(Li)( Δ t) Δ L = (1.8 x 10-^5 /ºC)(3 cm)(100ºC - 0ºC ) Δ L = 0.0054 cm

Lf = Δ L + Li Lf = 0.0054 cm + 3 cm Lf = 3.0054 cm

Linear Expansion Example

A glass jar ( = 0.3x10-5/ºC) has a metal lid ( = 1.6x10-5/ºC ) which is stuck. If you heat them by placing them in hot water, the lid will be:

(A) Easier to open

(B) Harder to open

(C) Same

Linear Expansion Example

A brass rod is 0.70 m long at 40ºC. Find the length of this rod at 50ºC.

Linear Expansion Example

The diameter of a hole drilled though a piece of brass is 1. cm at 20.0ºC. What is the diameter at 15.0ºC?

Linear Expansion Example

http://www.youtube.com/watch?v=fZaAqRS6uOM

J.S. Miller Video – Thermal Expansion

Volumetric Expansion

Amount of volume expansion (V) depends on the following:

1. T (Tfinal – Tinitial) : Change in temperature (ºC)
2. Vi : Original volume
3. Beta (): Coefficient of volumetric expansion

Units for Coefficient of Volumetric Expansion:  units: 1/ºC

Volumetric Expansion

V =  Vi T

Change In Temperature Final - Initial

Original Volume Coefficient Of Volumetric Change Expansion In Volume

Volumetric Expansion Formula