On Mar 25, 2005, at 4:26 PM, David Kirkby wrote:
> R. Measures wrote:
>
>>
>> On Mar 25, 2005, at 2:00 PM, David Kirkby wrote:
>>
>>> R.Measures wrote:
>>>
>>>>
>>>>>
>>>>> You can not find RMS power by multiplying RMS voltage by RMS
>>>>> current.
>>>>>
>>>>
>>>> I disagree. .
>>>>
>>>
>>> Rich, I think you are wrong. Here's my reasoning - I may well be
>>> wrong, as maths never was a good point of mine.
>>>
>>> You need to understand calculus to properly work out the RMS of an
>>> arbitrary waveform, as you probably know.
>>> Hence this explanation will really only be of use to someone who
>>> knows integration. But I can't see a simple way of computing the RMS
>>> value of the power, without it. People will just argue, but if you
>>> go back to first principles, you should get the right answer.
>>
>>
>> The right answer is that RMS current x RMS potential = AC P
>
> Any chance of you substantiating what you have said?
Does P = I x E?
>
> You stated you disagreed with Gary (K4FMX) who said
>
> > You can not find RMS power by multiplying RMS voltage by RMS
> current."
>
> Now I think you are wrong to disagree with K4FMX. I don;'t believe a
> simple multiple of the RMS values of voltage and current gives the rms
> power.
Chortle
>
> If you have 1V peak across 1 Ohm you have an RMS voltage of 0.707 V,
> and RMS current of 0.707A. If you multiply the RMS voltage by the RMS
> current you get 0.5W. (0.707*0.707=0.5). But I computed, and have
> fully justified, that the actual RMS power is 0.612273 Watts for a 1V
> peak. I don't think the term RMS power is very useful, but if you
> want to use the term, then at least use it correctly.
>
> I stuck a few notes at
>
> http://www.g8wrb.org/useful-stuff/index.html
>
> where you will find an html page on it
>
> http://www.g8wrb.org/useful-stuff/rmspower.html
>
> but its best to look at http://www.g8wrb.org/useful-stuff/index.html
> , as you can find other file formats, that are more useful.
>
> You have rather a habbit Rich of saying things without justification.
> Tell me where my analysis is wrong? Where is my mistake? I'm not
> saying there is no error (I admitted maths is not a strong point of
> mine) - but at least I don't dismiss other peoples comments and just
> think mine is right all the time. I try to substantiate what I say,
> rather than come back with one-liners that you expect everyone to take
> as gospel.
>
> --
> Dr. David Kirkby, G8WRB
>
> Please check out http://www.g8wrb.org/ of if you live in Essex
> http://www.southminster-branch-line.org.uk/
>
>
>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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