In article Tuno writes:
I can never keep these rules straight in my head, so I was happy to
find this cheat sheet:

http://www.evparts.com/img/voltsampsohmwatts.PDF

2NO /* software guy */


Caution, the section for watts is only correct for DC or purely resistive
loads. For AC, it falls short if you are using something more complex than
an incandescent light bulb.

The 3 phase comment at the bottom assumes you are measuring the voltages
phase to phase, and that the load is purely resistive, and equally
distributed along the phases, which is probably an unusual condition.

Alan