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Explaining the concept of Watt to me 
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#1
Nov2105, 04:25 PM

P: 357

A guy was explaining the concept of Watt to me, using a drawing of a machine that used 1 Joule per second, i.e. an oven. This one watt is now converted into heat, but excactly how much heat does 1 watt equal in terms of temperature? I'm not even sure if there is a relation, but if not, how is an oven of let's say 2 kW supposed to tell me anything of use?
Someone also told me that explaining this would require me to know the concept of enthalpy...anyone... 


#2
Nov2105, 05:25 PM

Mentor
P: 22,283

4.19 Joules = 1 Calorie = the amount of heat required to raise 1g (1mL) of water 1C.
So lets say a 1500W microwave oven is 50% efficient and you want to boil 1L of 20C water... 1000mL*80C*4.19=335,200J 335,200J/750J/s=447s=7.45 minutes 


#3
Nov2105, 09:17 PM

HW Helper
P: 660

Q = mCT where Q is the heat exchanged, m is the mass, C is the specific heat constant of the substance and T is the temperature change. So depending on what you're heating with that 2kW, you will end up with different temperature changes (e.g. it's easier to 1 gallon of air than 1 gallon of water). On another note, the 2kW does tell you something: how much you will be needing to pay on your electric bill ;) 


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