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J
jdirry1-Visitor
1-Visitor
November 28, 2016
Question

Subtracting Degrees Celsius

  • November 28, 2016
  • 14 replies
  • 7446 views

When subtracting two thermodynamic temperatures, like 3°C from 5°C, I expect to get the result in Kelvins:

5 °C-3 °C→ 2 K

However, Mathcad gives

5 °C-3 °C→ 2•°C


and doesn't handle it any different than a thermodynamic temperature, while it should handle it as temperature difference and therefore in absolute units (which is K) rather than in relative units.

Is there any way around this problem?

14 replies

W
Werner_E25-Diamond I
25-Diamond I
November 29, 2016

I don't experience that effect. Mathcad gives me exactly the 2 K which you expect and of course I could format the result in Delta °C if I like to do so. Changing the unit to °C would be wrong, of course:

J
jdirry1-VisitorAuthor
1-Visitor
November 29, 2016

I can replicate the problem in MathCAD Prime 3.1. The behavior you describe would be the correct one. Which version of MathCAD are you using?

mathcad prime 3.1 degrees celsius.pngmathcad prime 3.1 degrees celsius 2.png

R
RichardJ19-Tanzanite
19-Tanzanite
November 29, 2016

I can reproduce this in Mathcad Prime when using symbolic evaluation. The symbolic processor does not understand units, so you should use only numeric evaluation. However, it should not show a wrong answer, so I consider this to be a bug.

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