So let's see what the relationship is. So, let's finally examine and see what the relationship is between cell voltage and changing gear free energy. Well, we see that changing gear's free energy is equal to negative of electrical work done. Well, why is that? Well, this guy is simply the amount of free energy available to do useful work, while with this guy, the electrical work is the amount of energy transformed from chemical energy to electrical energy in the form of moving electrons. And this is also energy used to do useful work.