 Now we can look at a capacitor with a dielectric. So let's refresh our memory on what a capacitor looked like in a 3D view. And here we have our diagram labeling some of the pertinent features of it. So A is our plate area. D is our distance between the plates. And then you've got your dielectric. Or it could be empty space. Up to this point we've been dealing with a case where in between those two plates it was empty space. Now we're actually going to look at the case where we've got a dielectric in there. Now the equation here is got our capacitance. And it's related to this kappa epsilon naught A over D. Where A is our plate area. D is our distance between the plates. Epsilon naught is our electrostatic constant. And kappa is our dielectric constant. Now if we compare that just quickly to the equation without the dielectric we notice that it's almost exactly the same except for now we have the extra term a kappa in there. So let's take a look at those constants again. Our electrostatic constant, epsilon naught, is the permittivity of free space. And it's a fundamental constant that always has the value of 8.854 times 10 to the minus 12th Coulomb square per Newton meter squared. But this is the permittivity of free space. So I can use that if I've got nothing in there. Now kappa is our dielectric constant. And this is the Greek letter kappa. So it's not just a k, it's a Greek letter kappa in there. Looks very similar to a k though. It's a material specific constant. So the value varies from material to material. A kappa value of one is what we have for free space. Now it turns out that just plain air has a kappa that's almost exactly one. And so if we've got nothing between those two plates, we can use a kappa of one. If I've got another type of material, for example nylon, I might have a kappa of 3.4. Now I want you to notice there's no units here on kappa. It's a number value that has to do with how much our permittivity is changed from the free space to the case where there's dielectric in there. So this is our dielectric capacitor.