 Charge per day is given as sigma, that's nonsense now. You don't, you're not required to take that, it's just nonsense. Increase that, since 4 hour class is there. So last 45 minutes, we can have a small test. For 15 minutes, I'll discuss the test with you. Whatever we do on that day, I'll write down few questions. Take it like a test and we'll discuss it. Diage with those who don't hear anything. And those who have, I can write up questions and we'll discuss it. Because ultimately, when you struggle to solve a question, then only you learn. Or I solve one more. When you struggle. Okay, now tell me what is a potentiate due to this ring, of radius, small R and width, D R. How much is the charge on it? This is what sigma into 2 pi r which is K sigma 2 pi r d. So sigma into 2 pi into K comes out. Sigma into pi K you just take outside because 0 to r 2 r d is so little big. So that's what sigma into pi K is what 4 pi instead of 0. Now this here is due to be t. So when r this is z square z square. So this is d K sigma by 4 epsilon naught minus half plus 1. So you will get sigma by epsilon root z square on the disk. What will be the potential energy? That into this. Ct also in Ct, J e planes and as we know this they expect you to know. That is why I want you to know. I want you to find out potential irradiance r which is less than the radius of the. What will be the potential inside this big hollow sphere? In this constant charge its potential will be K u by r a point charge. If it is a ring if it is a disk we know what is the potential. Similarly there can be other type of charge distribution. We will be doing it once you get comfortable with the catalyst. And then due to the very charge distribution is a charge q at a potential energy. Understood this point? Potential due to charge and potential sorry of it due to charge potential as potential energy. When last chapter the previous chapter it was the outside electric field on the charge as force. When we did previous chapter we found the electric field due to a dipole. And then also found of external electric field. Now similarly we will be doing for potential external potential on the airport. Now lets try to find out potential. Till where this chapter is going to school? 1st chapter half. So I think there is 4 publications. So I think for next week 6 to 7 months. This Monday it will be there. This Monday it will be there. So and then 2 weeks of vacation? 2 months. 2 months so much study you can do right? Yeah. 2 months. 27 days. 27 days. 29 days. 2 months. So you have like 2 months as in 8 classes of presents. We will be this chapter next class. Next class of presents will be done. And then after that we will be doing more classes. So we can complete. And then we can maybe starting a 4th program. Like upper, middle, right? Oh 6 or 7 months. Anyways lets do this potential due to a dipole. And let me tell you again that these 2 chapters are considered to be the most difficult. So do this come back to this chapter again and again. Once you do these 2 chapters systemically work hard these 2 chapters. Rest everything in physics becomes very very straightforward. And then solve atleast 100 more questions. Then only you will get an idea. Don't just understand ok nothing but sports is there. Potential is there. Potential is there. Unless you solve a lot of questions you will not understand whatever varieties are there. Ok? Fine. So let's talk about a charge. This is minus charge suppose. This is like differential points like axial line and equatorial plane. Ok? So I write you connect a line like this. This line makes angle theta and the distance is r. This point p could be uniquely written like this. Ok? This is the middle point. Alright? Let me make a small instruction. Let's say r minus. So what should be the potential at point p? In terms of r plus and r minus. At that point. Take you from here. This is k and that distance is also k. This is theta.