1. The problem statement, all variables and given/known data Two isolated conducting spheres, each one with a radius of 14 cm, are charged until they reach the potentials of 240 V and 440 V. They are then connected by a thin wire. Calculate the variation of internal energy of the wire. 2. Relevant equations 3. The attempt at a solution When the wire is connected to both spheres, charge flows from the 240 V sphere to the 440 V sphere, in order to equal the potential. Since both spheres have the same radius, the final charge in each sphere will be equal. The final potential in each sphere will equal (240 + 440)/2 = 340 V. I think that the variation of internal energy is related to the fact that the potential difference between the ends of the wire changes from 200 V to 0 V as the charge flows through it. But I'm not sure how to proceed from here. Thank you in advance.