Joule’s Law

Joule’s Law is a physical law expressing the relationship between the heat (Q) generated by a current (I) flowing through a conductor of electrical resistance (R) over a given period of time (t).

Q=I^2Rt

I=\sqrt{\frac{Q}{Rt}}

R=\frac{Q}{I^2t}

t=\frac{Q}{I^2R}

More info: http://en.wikipedia.org/wiki/Joule%27s_law