Control

http://techteach.no/simview/index.htm

Resitor
http://www.hobby-hour.com/electronics/resistorcalculator.php

How much power can a wind turbine make?
http://www.windgenkits.com/faq.htm

Latex

Editor de ecuaciones con Latex
http://rinconmatematico.com/latexrender/
http://www.hamline.edu/~arundquist/equationeditor/