2.3 Thermodynamics 2.3.4 Thermal Properties and Processes
P2350400
Emittance of hot bodies (Leslie cube) What you can learn about ■■ Thermal radiation and emittance ■■ Kirchhoff‘s law of thermal radiation ■■ Leslie‘s cube ■■ Black and grey body
Benefits ■■ Simple set-up ■■ Affordable experiment ■■ For both demonstration and student experiments
Details
Principle Thermal radiation can be measured at all surfaces as long as their temperature differs from that of the surrounding. Therefore it applies that the hotter an object is, the more radiation it emits. Also the surface colour influences the behaviour: dark surfaces emit more thermal radiation than light ones. An example for application of this effect is a heat sink which is often coated with a black layer to emit more thermal radiation.
P3011400
Tasks 1. Measurement of the room temperature T0 (in Kelvin) before starting the experiment. 2. Determination and comparison of the emittance for all four sides of the Leslie cube at a constant high temperature. Determination and comparison of the emittance for all four sides of the Leslie cube depending on the temperature. 3. Plotting the thermoelectric voltage Vth as a function of the absolute temperature T or rather T4 - T04 for each side of the cube.
Condensation of gases through an increase of pressure and through cooling What you can learn about ■■ Condensation ■■ Gas laws
Benefits ■■ Compact setup ■■ Perfect as demonstration and student experiment ■■ Beautiful illustration of the phase transition from gaseous to liquid
Details
Principle Gases are condensing when they are cooled and at high pressure. In this experiment butane is condensed by cooling it to ca. -15 °C. In the second part of the experiment butane is condensed by compressing it.
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Tasks 1. Condense butane by cooling it under its boiling point of -0.4 °C. 2. Condense butane at high pressure.
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