Intro to electric potential

when you're walking on a street let's say somebody comes to you and say hey electric potential at some point in space let's call it pointer c is 20 world what is the meaning of that statement what would it mean so by the end of the video you'll be able to explain this statement in very simple terms to someone to begin with we are familiar with this word potential potential energy and we've learned of potential energy when it comes to gravity so let's start there say we held a five kilogram bowling ball in our hand and i know bowling balls are a little larger than this but imagine we held it at some distance from the ground then we say that it has potential energy why do we say that we say that because if i let go of that ball then it's as it falls down it's going to speed up speed up speed up and it's going to gain kinetic energy and we could ask where did that kinetic energy come from for example let's say at this point we calculate and we figure out that the kinetic energy at this point is i don't know maybe 55 joules and we don't have to worry about how to calculate that let's just take some random number we could ask hey where did this 55 joules come from where was this before because energy can neither be created nor destroyed and so we say ah this 55 joules was already stored in the ball before even before releasing it and that energy is what we call potential energy and so according to our example this ball now has a potential energy and the symbol we use for potential energy is usually u and we say the potential energy of this ball is that same 55 joules okay now here's my question to you my question is a five kilogram ball held at this point has 55 joules how much potential energy a one kilogram ball held at this same point have can you pause the video and think about this all right hopefully you've tried so you might know that less mass means less potential energy in fact if i have only one kilogram one-fifth of the mass then even the potential energy would be just one-fifth and so one-fifth of 55 would be just 11 joules all right and so you know what i can do now i can get rid of this ball and i could say at this point and i could put a indicator i mean i could i can label that point and say let's call it point a and i could say at this point the potential energy is 11 joules per kilogram that's how we can write and what this means is if i were to keep one kilogram over here it would have 11 joules of potential energy and this number how much potential energy you get per kilogram is what we call potential and we will write a over here because this is potential at point a and this is potential energy at point a so do you see the difference between them potential is just potential energy that one kilogram would have it's an indicator just like how when you go through grocery stores you have indicators over there which says hey 100 rupees per kilogram this means if you buy one kilogram you pay 100 rupees but it could also mean that if you buy three kilograms you have to pay 300 rupees and so on and so forth similarly it's an indicator which says hey if you keep one kilogram it would have 11 joules of potential energy but you could keep 10 kilograms over here and it would have 110 joules of potential energy so that's what gravitational potential is so this is gravitational potential similarly similarly we can now define electric potential so let me let me consider an electric potential case so let's say we have something very similar we have now a bowling ball which is charged because you want electricity and let's say it has 20 coulombs of charge a lot a lot of charge and let's say we have another huge charge which is negatively charged over here somewhere down over here and so now we have a situation which is very similar to that of gravity if i were to let go of my hand we know that that thing is going to get attracted towards this and let's assume this is fixed then for simplicity okay and then it's gonna get attracted and it's gonna gain kinetic energy and just like before let's take some random number let's say that it gains a kinetic energy of i don't know maybe 100 joules as an example we could ask hey where did this 100 joules kinetic energy come from right and then we could say ah that energy was already stored before and we could now say that all that hundred joules was stored as potential energy and i could now ask the same question as i did before if 20 coulombs of charge at this point has 100 joules of potential energy how much would one coulomb have at this point what'll be your answer well just like before it's going to be 100 divided by 20 coulomb it'll be 1 20th of that and so we can now write we can now get just like before we can now get rid of that wall i can put a label over there at that point and i could say ah at that point the potential energy would be 100 divided by 20 that is 5 joules per coulomb and this number is what we would call electric potential at point a so now again do you understand the difference between electric potential and electric potential energy potential energy uh potential is just potential energy that one coulomb would have it's an indicator all right so we can now define what electric potential is let me write that down over here so in general what is electric potential v say at any point p how do you define that we could say that's the potential energy sorry that quickly potential energy a one plus one we have to be careful about charges so that it's positive or negative you always consider plus as a standard a plus one coulomb charge would have would have its potential energy per coulomb and the way you calculate is you calculate you you take the potential energy and you divide by the charge to calculate how much you get per coulomb and the unit for that would be joules per coulomb but it turns out the joules per coulomb can is also called because it's used so often it's also called volt named after the physicist alessandro volta who discovered the very first we invented sorry who invented the very first battery okay so volt is just joules per coulomb and so now we can go back to our original question if somebody says at some point c just random point in space that potential at point c is 20 volt what is the meaning of this statement can you now explain this to someone pause the video and think all right we can now say hey first of all volt is joules per coulomb remember that and then you'll be fine so we could say this means it's 20 joules per coulomb and what it basically means it's saying that if you were to keep one coulomb of charge at this point it would have 20 joules of potential energy but it's an indicator so you can also mean that if you keep 10 coulombs of charge at this point it would have 200 joules of potential energy so remember potentials are just indicators that we can add to any point in space now of course before winding up i do want to mention that there are more than one ways to define electric potential and maybe the most standard definitions are different and we'll get to that so we'll talk more about what does it mean to have negative potential energy or negative potential what is potential difference we'll get to all that fun stuff in the future videos