In a general homework question I often encounter terms like "a wire of resistance R is stretched, what factor the power dissipated changes?" What exactly is this power dissipated ? Is it the one "wasted away" by heating up the wire due to the wire's resistance? or is it the power "used up" or transferred by the current conducted in the wire at certain voltage? For instance in the example above if the length of the wire is doubled uniformly , the power dissipated is then decreased. So, when we use a longer wire did we decrease the power dissipation? Do we have two power values for the same situation? P as I x V-power transferred- and P' as V^2/R-power dissipated- ?