 Let me just give you some analysis, for example, in class we have, it is of it you can study as two times, you can study the, so all that we are going to study in this particular topic. How many of you are not there? Anyways, in there it is potential energy, we have first understood the effect of the charges as electrostatic force, potential energy that will be in this chapter. Now before we even get into that, first potential energy, what is the definition of potential energy? Potential energy divided by the energy of it, so inside it is force, so we should know how can we derive the expression for potential energy for a particular force. Do you remember how we defined the expression for potential energy for any force? Do you remember? If you define it, what do you mean by potential energy? I wanted to define the potential energy of a potential energy force, what is the process of defining it, so that we will be able to do it more easily. Now can we, how much work is done by the gravity over here? Fine, for gravity type, you cannot multiply force with this specimen. So you cannot just multiply, let me take example of, you might be wondering why this topic is the electrostatic potential, but then we are talking about the electrostatic potential energy. Just like first we have defined what is force and then force per unit charge was free. Similarly here, first we will define potential energy and then we will say that potential energy per unit charge is potential. Now suppose this is the scenario, you have a Q1, from this point the charge is slowly moved to that point. This Q2 has moved from R2 distance to R2 distance from a fixed charge Q1. Now my simple question is the force of initial charge is same probe, yes or no? So force is not between the two charges of force. Now suppose Q2-Q1, Q2 is potential energy, this is equal to Q2-Q1, Q4-Q2. You cannot change your answer because when you, in fact something which is energy, you have to assume stuff, you may say your charges is very large. We are going to take Q1-Q2 by R, this is the potential energy between the two charges. This is not the potential energy of Q1 or potential Q2. Q1-Q2 is potential, clear?