reference is called absolute zero. His scale starts at absolute zero and reads upward in
degrees Kelvin. Each Kelvin degree is equivalent to a Celsius degree. Actually 0,K is -
273.16,C, but for general measurements the value -273,C is used. The advantage of the
Kelvin scale is that all temperatures are positive with respect to absolute zero.
Now lets try to convert from one temperature scale to another. What would a Celsius
scale read if a Kelvin scale measuring the same temperature indicates 273,?
If your answer is 0, Celsius is equivalent to 273, Kelvin I warmly agree with you
Subtracting 273 from a Kelvin scale value will result in the equivalent Celsius scale
value.
273,K minus 273 = 0,C.
A picture is worth a thousand words. Now, notice the relationship between the Kelvin
and Celsius (centigrade) scales.
Remember! To convert from ,K to ,C subtract 273 from the Kelvin reading.
Example: 200,K minus 273, = -73,C.
Lets try another problem. What temperature on the Kelvin scale would be equivalent to
the steam point of water?
There are two ways of obtaining the answer:
1. To convert N degrees Kelvin to degrees Celsius, subtract 273,K from N degrees
Kelvin.
2. Knowing the steam point of water is 100,C, add 273 to find the temperature above
absolute zero. For example, 100,C, + 273 = 373,C.
What is -40,C in terms of the Kelvin scale? It is easy to convert between degrees Kelvin
and degrees Celsius. Since ,K = ,C + 273, we have ,K = -40 + 273, hence K = 233,.
As pointed out before, the Kelvin scale readings are all positive in respect to absolute
zero. The Kelvin scale is used frequently in scientific work, especially in the (-),C
region.
There are two other temperature scales worth discussing, because they are in common use
throughout the English speaking countries.
9. FAHRENHEIT SCALE.
Thermometers used for everyday household use are calibrated in degrees (F) Fahrenheit.
The Fahrenheit scale divides the difference between the ice point and steam point of
water into 180 increments.
Compare 180,F to 100,C, between the same reference points, and you will notice a 9/5
relationship. Another relationship is that 32,F is equivalent to 0 C, while the steam point
of water is 212,F. (Refer to figure 10)
Previous Page
