8.02x - Lect 1 - Electric Charges and Forces - Coulomb's Law - Polarization
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it when asking about or explaining electrostatics demos such as charge transfer from rubbing, polarization and induction.
Recommended by 1 people across 1 different months, 2018 to 2023.
What it is
The first lecture of Walter Lewin's MIT 8.02 electricity and magnetism course. It covers the history of electric charge, polarization, electric force and Coulomb's Law, with classroom demonstrations including a Van de Graaff generator. Lewin presents it live to a lecture hall.
What people said
Recommends basics · 2022-12 · Physics Stack Exchange · on “Is there any third charge in paper or is it neutral?”
No there is no third charge, but there is electrostatic induction , i.e. a redistribution of electric charge in an object that is caused by the influence of nearby charges. Pieces of paper are approximately electrically neutral, i.e. not net charge in them, but the influence of charged rods influence the distribution of charges on in, attracting opposite and repelling equal-sign charges. Since the distance between the opposite charges is smaller than the distance between the equal-sign charges, you get an attractive force, whatever the nature of the extra charges on the rod is. Since paper is not a good conductor, or better it's a dielectric , you should not think at macroscopic displacement
Cites HsMjstyMstdn · 2018-01 · Physics Stack Exchange · on “Question about static cling”
Roughly speaking, when something (object A) is rubbed against something else (object B), some of that rubbing-energy (friction) makes electrons jump from one object to another. We call this triboelectrification. The wiki [LINK] gives a basic overview. Although this effect has been known for thousands of years, it is not fully understood from a fundamental aspect. Its exact working mechanism is debated with some models showing thermal excitation playing a role, some suggest an "abundance effect" property of materials, some say mechanical stress and agitation produce free radicals with high-enough energy electrons, etc. This is somewhat due to the lack of generalised predictability of models a
Cites S_M · 2023-12 · Physics Stack Exchange · on “Electrostatics (Waler Lewin's Lectures): Cat-fur, Nylon Jackets, and Charges”
[this video] Please consider the above video from 24:15-25-32 . I would like to understand how the charge is being transferred through the flashtube. First, Walter beats the student with a cat-fur napkin, or whatever. This removes electrons from the jacket the student is wearing and transfers it to the cat-fur napkin, or vice-versa, does not really matter. Then they both hold a flash tube, and charge flows, owing to the potential difference between Walter's fingers and the student. When Walter beats the student with the napkin, only the napkin and the student's jacket get charged. Assume, the napkin gets negatively charged, and the student's jacket positively charged. So, only the student's jacke