What is the Kelvin Scale
When we discuss what is the meaning of kelvin or what is the kelvin temperature scale, we refer to it as the temperature scale which uses Kelvin or K for denoting the magnitude of temperature. It is the SI unit of temperature and is named after Sir William Thomson, an engineer and physicist.
What is Kelvin Based On
In 1848, William Thomson, later known as Lord Kelvin, had written a paper “On an Absolute Thermometric Scale”, for needing a scale where infinite cold, now known as absolute zero, could be defined as the scale’s null point, and used degree Celsius for every unit increase.
He found that the absolute zero value on air thermometers was -273 °C. This was regarded as the absolute value, which is known as the Kelvin temperature scale. The value -273 of the Kelvin scale is referred to as the negative reciprocal of 0.00366. This is known as the gas expansion coefficient per one degree Celsius which is relative to the ice level.
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What is Kelvin Used For
Let us discuss what is Kelvin temperature and what are its applications.
Kelvin temperature is used for measuring the temperature of the colours that are associated with the light sources. The colour temperature is dependent on the idea that the back body radiator emits light having temperature characteristics similar to the frequency distribution. These blackbodies appear reddish in colour below 4000 K temperature and bluish in colour above 7500 K. this concept of colour temperatures plays an essential role in image projection and photography in which the temperature of the colours equal to 5600 K is required for matching the emulsions of the daylight films.
In the field of astronomy, the position and the stellar classification of the stars in the Hertzsprung – Russell diagram depend partially on their surface temperatures, which is also called as the effective temperature. An example of this is that the photosphere of the Sun has 5778 K as its effective temperature.
Kelvin temperature scale is also useful in electronics for measuring how noisy a circuit is relative to its noise temperature, or the ultimate noise levels.
What is the Boiling Point of Water in Kelvin
The boiling point of water in Kelvin is 373 K.
What is the Freezing Point of Water in Kelvin
The freezing point of water in Kelvin is 273 K.
What is 1 Kelvin
Let us discuss what is the formula of Kelvin.
1K − 273.15 = -272.1°C
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Now that we know what does kelvin mean, let us discuss about what is the Celsius scale and what is the formula to convert Celsius to Kelvin.
What is the Celsius Scale
The Celsius temperature is also known as the Centigrade scale and it was developed depending on the boiling point and the freezing point of water. Celsius is also an SI derived temperature unit. The Celsius scale is the most preferred scale for measuring temperatures in our day to day lives.
Development of the Celsius Scale
In 1742, a Swedish astronomer and physicist Anders Celsius had developed a temperature scale, exactly opposite to the Celsius scale. According to this scale, the boiling point of water was 0 ℃ and the freezing point of water was 100 ℃. He also wrote a paper on the same in which he mentioned his observations from the experiments he conducted stating that the melting point of ice is unchanged even when there is variance in the pressure. He also calculated the variations in the boiling point of water with the changes in the atmospheric pressure.
From 1743, the Celsius temperature scale changed and the boiling of water was kept as 100 °C and the freezing point of water was kept as 0 °C at a pressure of 1 atm. This reversal of the Celsius temperature scale was proposed by Jean-Pierre Christin, a French physicist.
Conversion of Celsius to Kelvin
The formula to convert Celsius to Kelvin is given below.
0 degrees Celsius equals 273.15 Kelvins or 0°C + 273.15 = 273.15K
Hence, the formula is °C + 273.15 = K.
FAQs on Kelvin Scale and Celsius Scale
1. What is the fundamental difference between the Celsius and Kelvin temperature scales?
The primary difference lies in their zero points. The Celsius scale sets 0°C as the freezing point of water, a relative benchmark. In contrast, the Kelvin scale uses Absolute Zero (0 K) as its starting point, which is the theoretical temperature at which all molecular motion ceases. While their starting points differ, the magnitude of a one-degree change is identical on both scales.
2. What is the formula to convert a temperature from Celsius (°C) to Kelvin (K)?
To convert a temperature from Celsius to Kelvin, you add 273.15 to the Celsius value. The formula is: K = °C + 273.15. For most school-level calculations as per the CBSE syllabus, this is often simplified to K = °C + 273. For example, a room temperature of 25°C is equivalent to 25 + 273.15 = 298.15 K.
3. How do you convert a temperature from Kelvin (K) back to Celsius (°C)?
To convert a temperature from Kelvin back to Celsius, you subtract 273.15 from the Kelvin value. The formula is: °C = K - 273.15. For example, the boiling point of water is 373.15 K, which converts to 373.15 - 273.15 = 100°C.
4. What are the freezing and boiling points of water on both the Celsius and Kelvin scales?
The freezing and boiling points of water are key reference points for both scales:
Freezing Point of Water: It is 0°C on the Celsius scale, which corresponds to 273.15 K on the Kelvin scale.
Boiling Point of Water: It is 100°C on the Celsius scale, which corresponds to 373.15 K on the Kelvin scale.
This demonstrates the 100-unit interval between these two points on both scales.
5. Why is the Kelvin scale called the 'absolute' temperature scale?
The Kelvin scale is called the 'absolute' temperature scale because its zero point (0 K) is Absolute Zero, the lowest possible temperature that can exist in the universe. At this temperature, particles have minimal kinetic energy. Unlike the Celsius or Fahrenheit scales, which have negative values, the Kelvin scale has no negative numbers. This makes it directly proportional to the thermal energy of a system, a crucial feature for scientific laws.
6. Why is a one-degree change the same on both the Celsius and Kelvin scales?
A one-degree change is the same on both scales by definition. The Celsius scale was established by dividing the temperature range between water's freezing and boiling points into 100 equal parts. When the Kelvin scale was developed, it was intentionally calibrated to match this same interval size for consistency. Therefore, a temperature increase of 1°C is precisely equal to a temperature increase of 1 K; they just have different starting references.
7. Can the Celsius and Kelvin scales ever show the same numerical reading for a temperature?
No, the Celsius and Kelvin scales can never show the same numerical value. This is due to the constant offset of 273.15 units between them (K = °C + 273.15). For the readings to be equal (where K = °C), it would require 273.15 to be zero, which is mathematically impossible. The two scales run parallel to each other but never intersect.
8. Why do scientists prefer using the Kelvin scale for calculations in chemistry and physics?
Scientists prefer the Kelvin scale for several key reasons:
Absence of Negative Values: It eliminates the complication of using negative numbers in scientific formulas, such as the gas laws (e.g., Charles's Law, Ideal Gas Law).
Direct Proportionality to Energy: Temperature in Kelvin is directly proportional to the average kinetic energy of the particles. For instance, a substance at 200 K has twice the kinetic energy of the same substance at 100 K. This direct relationship does not hold for the Celsius scale.
Fundamental Basis: Its zero point is based on a fundamental constant of nature (Absolute Zero), not an arbitrary property of a substance like water.
