When to convert units of temperature?

In summary,- radiation and conduction depend on temperature.- You convert from K to oC when you need to.
  • #1
BlackJ
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1

Homework Statement


[/B]
(1)A sphere of radius 0.500 m, temperature 27.0 C, and emissivity
0.850 is located in an environment of temperature 77.0 C. At
what rate does the sphere (a) emit and (b) absorb thermal radiation?
(c) What is the sphere’s net rate of energy exchange?

(2)A cylindrical copper rod of length 1.2 m and cross-sectional
area 4.8 cm2 is insulated along its side.The ends are held at a temperature
difference of 100 degree C by having one end in a water–ice mixture
and the other in a mixture of boiling water and steam. At what rate
(a) is energy conducted by the rod and (b) does the ice melt?

Homework Equations

The Attempt at a Solution


So I'm studying the chapter about temperature, heat and the first law of thermodynamics. I start to feel confused about when the temperature should be converted. Sometimes it's Celsius sometimes it's in Kelvin. For example, could anyone explain why the first problem have to convert to Kelvin but the second one can be in Celsius?
 
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  • #2
I hope someone like Chester comes along, who is an expert in thermodynamics, as I'm not.
But I think the answer here is straightforward.

In 1) radiation depends on the absolute temperature, so you convert to K.
( Only at absolute 0 is there no radiation. Just because something is at 0 oC, it is not incapable of radiating heat.)

In 2) conduction depends on temperature difference - which will be the same in K as it is in oC.
( You could even work in o F if you wanted, but you'd need to use a value for the conductivity expressed in those units.)
 
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  • #3
Same with what Merlin said. My rule is that you can pretty much exclusively use Kelvin in Physics because you can't go wrong with it; differences will be the same and relating things will be much easier, so it's nice to convert straight from the beginning. (Celsius + 273)
 
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Related to When to convert units of temperature?

1. When should temperature units be converted?

Temperature units should be converted when communicating or comparing measurements with others who use a different unit system. It is also important to convert units when performing calculations involving temperature.

2. What are the most commonly used temperature units?

The most commonly used temperature units are Celsius (°C), Fahrenheit (°F), and Kelvin (K). These units are used in different parts of the world and in different fields of science.

3. How do I convert between Celsius, Fahrenheit, and Kelvin?

To convert from Celsius to Fahrenheit, use the formula °F = (°C × 9/5) + 32. To convert from Fahrenheit to Celsius, use the formula °C = (°F - 32) × 5/9. To convert from Celsius to Kelvin, add 273.15 to the Celsius value. To convert from Kelvin to Celsius, subtract 273.15 from the Kelvin value.

4. Why is it important to use the correct temperature units in scientific research?

Using the correct temperature units in scientific research is important because it ensures accuracy and consistency in data analysis and communication. Using the wrong units can lead to incorrect conclusions and hinder the progress of research.

5. Are there any online tools or resources available for converting temperature units?

Yes, there are many online tools and resources available for converting temperature units. Some examples include unit conversion websites, scientific calculators, and conversion apps. It is important to double-check the accuracy of the tool or resource being used.

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