8.02x - Lect 8 - Polarization, Dielectrics, Van de Graaff Generator, Capacitors
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it to explain how a dielectric polarizes inside a capacitor and to point at the disassembled-capacitor demonstration.
Recommended by 2 people across 2 different months, 2016 to 2020.
What it is
Walter Lewin's MIT 8.02 lecture on electricity and magnetism covering polarization of dielectrics, the Van de Graaff generator, and more on capacitors. It ends with a mystery demonstration using a disassembled Leyden jar capacitor, shown on a blackboard-and-demo lecture hall format.
What people said
Recommends GeeJay · 2016-08 · Physics Stack Exchange · on “Potential of a planar capacitor with embedded electret”
No, the problem is this: there's a capacitor like any other, with opposite signed charge on either plate. A dielectric of thickness d is inserted into it. The electric field of the capacitor induces polarization in the dielectric, so that there is a layer of surface charge on opposite surfaces of the dielectric. Watch the first ten minutes of this [this video]
Recommends Rew · 2020-06 · Physics Stack Exchange · on “Dielectric permittivity”
I recently learned about the dielectric that is used between the plates of a capacitor. If $E_0$ is electric field between the plates of capacitor in free space and $E_i$ is electric field due to induced charge in a dielectric after it is inserted inside the capacitor, (Let the dielectric constant be $K$ ) It is known that electric field becomes $\dfrac{E_0}{K}$ . That is, $$\frac{E_0}{K} = E_0 - E_i$$ Now from where I studied it, they use $\sigma_i$ as charge density of induced charge. And write $E_i=\dfrac{ \sigma_i}{\epsilon_0}$ $\epsilon_0$ being the permittivity of free space. What I don't get is why use the permittivity of free space instead of permittivity of dielectric material? Afte
Cites Krish Vasa · 2020-07 · Physics Stack Exchange · on “How does a Capacitor generate a potential difference even after disassembling the Capacitor?”
I saw a video of Walter Lewin on YouTube in which he was showing a demonstration on Capacitors. In this demonstration, he gives a charge to the Capacitor, dissembles it and reconstructs the Capacitor. But after removing the charges also, the Capacitor still holds a potential difference. How is that possible? The video [this video] The demonstration starts at 39:00