2002-03-26 It just goes to show you how coherent SI is. The watt is defined relative to mechanical units because mechanical units form most of the base units for SI.
John ----- Original Message ----- From: "Joseph B. Reid" <[EMAIL PROTECTED]> To: "U.S. Metric Association" <[EMAIL PROTECTED]> Sent: Tuesday, 2002-03-26 10:48 Subject: [USMA:19075] Re: watt seconds ?? Bill Hooper wrote in USMA 19071: >The watt is also equal to a volt-ampere but that is not it's original >definition. The watt is originally defined as a joule per second. Since the >volt (V) is a joule per coulomb (J/C) and the coulomb (C) is defined as an >ampere-second (A�s), it is easy to show that the volt-ampere equals the >watt: >1 V�A = (1 J/C)�(1 A) = (1 J/A�s)�(1 A) = 1 J�s = 1 W > >(In proper SI, multiplication of units is shown by the raised dot. The >raised dot generated by my computer is shown here >between the letters X and Y: Bill has brought volts, coulombs and amperes into the discussion. Those are electrical units. The watt is defined in terms of length, mass and time (m2.kg/s3). The same is true of the joule (m2.kg/s2) Joe Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
