Re: [Phys-l] water heating - recap

[Brian Whatcott <betwys1@sbcglobal.net>]

I wrote earlier:
> I calculated the input power to produce this result as 91 watts into 
> 176.3 g. water. The wattmeter was indicating 84 watts for this. 
> Checking the heaters, I reada resistance of 195 ohms, and the input 
> voltage 121 V.This should have provided a heating rate of 75 watts. 
> This complete lack of agreement put a stop to the next phase...So much 
> for the joys of H.S. experimental procedure.....
I finally twigged the problem, though I had not provided enough clues 
for you to easily guess what
it was.  I noticed that the connecting wires for the heating resistors 
were discolored.
I coated the bare wires with epoxy, and tried again with distilled water.
This time the least squares straight line was 0.12028 deg per second 
into 150.0 gm water.
This provided a heating input estimate of 75.4 watts
The wattmeter indicated  73 watts and the Vsq/R amounted to 74 watts.
Much more the discepancy you might expect....
I had not accounted for the electrolytic heating before.
Ho hum....

BrianW