## Kelvin Scale

The Kelvin temperature scale (K) was developed by Lord Kelvin in the mid 1800s. The zero point of this scale is equivalent to -273.15 °C on the Celsius scale. This zero point is considered the lowest possible temperature of anything in the universe. Therefore, the Kelvin scale is also known as the "absolute temperature scale". At the freezing point of water, the temperature of the Kelvin scale reads 273 K. At the boiling point of water, it reads 373 K.

Whereas the Kelvin scale is widely used by scientists, the Celsius or Fahrenheit scales are used in daily life. These two scales are easier to understand than the large numbers of the Kelvin scale. Could you imagine waking up to your radio and hearing the DJ give a weather report like this: "It's going to be a beautiful day today with sunny skies and a balmy temperature of 297 K!" That's 24 °C or 75 °F.

## Kelvin Scale

The Kelvin temperature scale (K) was developed by Lord Kelvin in the mid 1800s. The zero point on this scale is base on the point at which the pressure of all dilute gases mathematically project to zero from the triple point of water (see graph at left). Recall that the triple point is the temperature at which liquid water, ice, and water vapor can coexist simultaneously.

The zero point of this scale is equivalent to -273.15 °C on the Celsius scale. This zero point is considered the lowest possible temperature of anything in the universe. Therefore, the Kelvin scale is also known as the "absolute temperature scale". At the freezing point of water, the temperature of the Kelvin scale reads 273 K. At the boiling point of water, it reads 373 K.

Lord Kelvin developed this scale with the help of a Carnot engine. The Carnot engine deals with the relationship between pressure, work, and temperature. The Carnot engine is the most efficient engine possible. However, even it cannot reach 100% efficiency. If an engine was 100% efficient, no energy would be wasted. The Carnot engine is only theoretical, which means that all real engines are even less efficient. To learn more about Carnot engines, go to your local library and look for books on the fundamentals of physics or thermodynamics.

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