Usually there is a change in voltage on the processor when the processor changes state. This change in voltage expends energy due to the capacitance of the pow

Usually there is a change in voltage on the processor when the processor changes state. This change in voltage expends energy due to the capacitance of the power rail and the circuit itself (the capacitance of one transitor itself is small but there are billions of them). http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng2.html http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng2.... Even if there is no change in voltage usually the processor will just leak power while making no forward progress on the program while the various timing circuits change.