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 * N/A  * This demonstration requires a supply of methane gas usually provided by the [:RedWhiteGasCarts: red and white gas carts] found in rooms 2103, 2241, (and 2223 upon request).
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 1. Choose a rod and place it on the holder.
 1. Connect the burner to the methane supply.
 1. Open the valve to let the gas flow, and light the burner using a match or lighter.
 1. Place the flame under the rod to heat it.
 1. Note the rate of expansion.
 1. Turn of the gas by closing the valve, and allow some time for the rod to cool.
 1. Carefully (using insulated gloves) switch out this rod for another one and repeat the heating process.
 1. Note that the rate of expansion for this different material is different from the first rod.
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Note: Make sure that one of the red & white gas cart are in placed and the gas hose is connected to the utility trench gas line. The gas cylinder that supplies the gas to utility trench gas line may or may not be connected/installed and should be inspected.
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 1. Beware of the heated rods - they can cause serious burns!
 1. Wear the safety grove and glasses.		  * Beware of the heated rods - they can cause serious burns!
 * Wear the safety grove and glasses.
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 This demonstration show that different materials have different [http://en.wikipedia.org/wiki/Coefficient_of_thermal_expansion coefficient of thermal expansion]. Once you choose a rod and place it on the holder, turn on the gas source to heat the rod. You will see that the orange tip scale will move to the left at some amount of rate. Then choose other rod in place of the previous one and heat it. The orange tip will move to the left at different rate.  A given material of given length (1D), area (2D), or volume (3D) will have different geometric size at different temperatures. The equations describing this behavior is

 ΔL/L = α,,L,,*ΔT (1D)

 ΔA/A = α,,A,,*ΔT = α,,L,,^2^*ΔT (2D)

 ΔV/V = α,,V,,*ΔT = α,,L,,^3^*ΔT (3D)

where L, A, and V are the initial length, area, and volume respectively when the material has temperature T,,i,,. The Δ denotes the change in that quantity (final - initial). α,,L,,, α,,A,,, α,,V,, are the linear, area, and volumetric coefficients of thermal expansion respectively. Note that for the 2D and 3D cases, equating α,,A,, to α,,L,,^2^ and α,,V,, to α,,L,,^3^ is only valid for small expansions (or contractions) in isotropic materials.

This demonstration shows that different materials have different coefficients of thermal expansion. We have two different materials that start at room temperature and are heated to the temperature of the flame. Thus, ΔT is the same for all the rods You will see that the orange tip scale will move to the left at some rate. Then choose another rod in place of the previous one and heat it. The orange tip will move to the left at different rate.

our available materials with their respective linear thermal expansion coefficients in ascending order
||'''Material'''||'''α,,L,, (x 10^-6^ K^-1^)'''||
||Kovar|| 5.5 ||
||Titanium|| 8.6 ||
||Cold-rolled steel|| 12.4 ||
||Nickle|| 13.0 ||
||Brass|| 18.7 ||

[:PiraScheme#Thermodynamics: Table of Thermodynamics Demonstration]

[:TDEquipmentList: Thermodynamics Equipment List]

[:Demonstrations:Lecture Demonstrations]

Thermal Expansion of Metal Rods , 4A30.58

Topic and Concept:

Location:

attachment:photo

Abstract:

This can also be called expansion rods. A metal blue box with various rods of different materials.

Equipment

Location

ID Number

Metal blue box with rods

[:ThermoCabinetBayA3: TD, A3, Shelf #1]

4A30.58

Safety glove and glasses

Important Setup Notes:

  • This demonstration requires a supply of methane gas usually provided by the [:RedWhiteGasCarts: red and white gas carts] found in rooms 2103, 2241, (and 2223 upon request).

Setup and Procedure:

  1. Choose a rod and place it on the holder.
  2. Connect the burner to the methane supply.
  3. Open the valve to let the gas flow, and light the burner using a match or lighter.
  4. Place the flame under the rod to heat it.
  5. Note the rate of expansion.
  6. Turn of the gas by closing the valve, and allow some time for the rod to cool.
  7. Carefully (using insulated gloves) switch out this rod for another one and repeat the heating process.
  8. Note that the rate of expansion for this different material is different from the first rod.

Cautions, Warnings, or Safety Concerns:

  • Beware of the heated rods - they can cause serious burns!
  • Wear the safety grove and glasses.

Discussion:

  • A given material of given length (1D), area (2D), or volume (3D) will have different geometric size at different temperatures. The equations describing this behavior is

    ΔL/L = αL*ΔT (1D)

    ΔA/A = αA*ΔT = αL2*ΔT (2D)

    ΔV/V = αV*ΔT = αL3*ΔT (3D)

where L, A, and V are the initial length, area, and volume respectively when the material has temperature Ti. The Δ denotes the change in that quantity (final - initial). αL, αA, αV are the linear, area, and volumetric coefficients of thermal expansion respectively. Note that for the 2D and 3D cases, equating αA to αL2 and αV to αL3 is only valid for small expansions (or contractions) in isotropic materials.

This demonstration shows that different materials have different coefficients of thermal expansion. We have two different materials that start at room temperature and are heated to the temperature of the flame. Thus, ΔT is the same for all the rods You will see that the orange tip scale will move to the left at some rate. Then choose another rod in place of the previous one and heat it. The orange tip will move to the left at different rate.

our available materials with their respective linear thermal expansion coefficients in ascending order

Material

αL (x 10-6 K-1)

Kovar

5.5

Titanium

8.6

Cold-rolled steel

12.4

Nickle

13.0

Brass

18.7

attachment:photos

attachment:photos

attachment:photos

attachment:photos

Videos:

References:

[:Instructional:Home]

fw: MetalRods (last edited 2021-02-09 17:31:36 by srnarf)