 Thermodynamics 2
The actual name 'thermodynamics,' is a term that emphasizes the movement (dynamics) of particles caused by heat (thermal motion). Cold and heat don't actually exist in thermodynamics. There are only
vibrations of
molecules of varying intensity. This starts at -273°C (459.4°F) and has no upper limit for us at this point. In the same way, we can't predict the speed at which people will move from place to place in a hundred
years.
| Temperature difference causes heat flow. |
But why isn't the point at which the molecules no longer move and below which temperature cannot be descended zero? Because the inventor of the Celsius scale couldn't yet determine this point. He simply
determined the melting point of water under normal pressure, which also persists throughout the entire melting process, as 0°C (68°F) and the boiling point of water, which also persists for a longer period, as
100°C (212°F).
| 0°C (32°F) corresponds to 273 K |
Then a W. Thomson, later Lord Kelvin, based the scale on absolute zero, but at least retained the Celsius intervals. Nevertheless, it is not called ° (degree) 'Kelvin,' but simply 'Kelvin.' 0 K(elvin) thus corresponds to -273.15°
C, -273.16°C, or 273.0075°C (approx. -459.67°F), although we will omit the decimal places. The zero point is theoretical, because what medium could be colder to cool another to this temperature?
| Approx. -50°C (-58°F) to 50°C (122°F) air temperature possible in the car. |
Temperatures are measured with thermometers, which measure the expansion of a liquid in a capillary tube. Larger fluctuations occur with alcohol, and smaller ones with mercury, which is highly toxic. The thermometer
obtains its scale by comparing it with a calibrated measuring device.
Temperature is usually measured electronically using a resistor with the properties of a Negative Temperature Coefficient, meaning its resistance value decreases with increasing temperature. A
commonly used reference value in the past was 2.3 kOhm at 20°C (68°F).
While an NTC is a cost-effective component, its proper functioning is also of utmost importance in air conditioning systems. As with a combustion engine, a malfunction can cause significant disruption. Usually, there are
other sources for the control unit to check, so it can at least be switched to emergency mode.
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