Find the maximum thermodynamic efficiency

[kelvin56484984]

Homework Statement

If an engine operates between 250°C and 25°C, what is its maximum thermodynamic efficiency?

Homework Equations

Ec=1-Tc/Th

The Attempt at a Solution

1-25/250
=90%
or
1-(25+273)/(250+273)
=43%

In this question,which one should I use K or ºC ?
thank you

 

[SteamKing]

Homework Statement

If an engine operates between 250°C and 25°C, what is its maximum thermodynamic efficiency?

Homework Equations

Ec=1-Tc/Th

The Attempt at a Solution

1-25/250
=90%
or
1-(25+273)/(250+273)
=43%

In this question,which one should I use K or ºC ?
thank you

What does Carnot's Theorem say about this?

https://en.wikipedia.org/wiki/Carnot's_theorem_(thermodynamics)

 

[mfig]

If you always use Kelvin you will avoid ever worrying about this again. Always just convert to Kelvin before doing anything else and you won't go wrong. The only time to use Celsius in thermodynamics or heat transfer is if the question want the answer in Celsisus - in that case convert to Celsius at the very last step after using Kelvin for calculations.