If you have two charges q1 and q2, you can get the force between them F by multiplying them with the coulomb constant K (approximately 9 × 10^9) and then dividing that by the distance between them squared r^2.
q1 and q2 cannot be negative. Sometimes you'll not be given a charge, and instead the problem will tell you that you have a proton or electron, both of them have the same charge (1.6 × 10^-19 C), but electrons have a negative charge.
In this case yes, but if q1 was -20μC, q2 was 30μC, and r was 0.5m, then using -20μC as it is would make F equal to -21.6N which is just 21.6N of attraction force between the two charges.
If there's anyone who can, please let me know if the similarities between these two formulas imply a relationship between gravity and electrical attraction or hint at a unified theory, or if it's just a coincidence or a consequence of something else.
The relation between them is that they're both forces that scale with the inverse square of the distance between the objects. Any force that scales with the inverse square of distance has pretty much the same general form.
Another similarity is that both are incomplete, first approximations that describe their respective forces. The more complete versions are Maxwell's laws for electromagnetism and General Relativity for gravity.
There is one thing particularly interesting, and that is that the inverse square laws appears again. It appears in the electrical laws for instance.
That is electricity also exerts forces inverse to the square of distance with charges. One thinks perhaps inverse square distance has some deep significance, maybe gravity and electricity are different aspects of the same thing
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Today our theory of physics, laws of physics are a multitude of different parts and pieces that don't fit together very well. We don't understand the one in terms of the other. We don't have one structure that it's all deduced we have several pieces that don't quite fit yet.
And that's the reason in these lectures instead of telling you what the law of physics is I talk about the things that's common in the various laws because we don't understand the connection between them.
But what's very strange is that there is certain things that's the same in both
Awesome to see the similarities between: Newtonian Mechanics and Quantum mechanics
Coulomb's law was essential to the development of the theory of electromagnetism and maybe even its starting point, as it allowed meaningful discussions of the amount of electric charge in a particle.
Here, ke is a constant, q1 and q2 are the quantit>ies of each charge, and the scalar r is the distance between the charges.
Being an inverse-square law, the law is similar to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces always make things attract, while electrostatic forces make charges attract or repel. Also, gravitational forces are much weaker than electrostatic forces. Coulomb's law can be used to derive Gauss's law, and vice versa. In the case of a single point charge at rest, the two laws are equivalent, expressing the same physical law in different ways. The law has been tested extensively, and observations have upheld the law on the scale from 10−16 m to 108 m.
"X depends on or is built up on Y" does not imply "X is Y". Concepts, laws, techniques, etc. can depend or be higher-order expressions of QM without being QM. If you started asking a QM scientist about tensile strength or the Mohs scale they would (rightly) be confused.
Yes, of course. Coloumb and Maxwell had no idea about QM when they were developing their ideas. Not to mention that these higher-order abstractions are just as valid as QM (up to a point, but so is QM). Depening on the application, you'd want to use a different abstraction. EM is perfect for everyday use, as well as all the way down to the microscale.
My point is that EM is explained by QM, and therefore supercedes it. You could use QM to solve every EM problem, it'd just be waaaaay too difficult to be practical.
I feel like you're using "supercede" differently to the rest of us. You're getting a hostile reaction because it sounded like you're saying that EM is no longer at all useful because it has been obsoleted (superceded) by QM. Now you're (correctly) saying that EM is still useful within its domain, but continuing to say that QM supercedes it. To me, at least, that's a contradiction. QM extends EM, but does not supercede it. If EM were supercedes, there would be no situation in which it was useful.
