# Tagged Questions

33 views

### How you call the constant $\alpha$ within the heat equation in general and in terms of electromagnetism?

The heat equation or diffusion equation does contain a constant $\alpha$. $$\frac{\partial u}{\partial t} - \alpha \nabla^2 u=0$$ How is it called? I'm interested in a general name which can be ...
55 views

### Why do we take the value of the constant in Coulomb's law as $\frac{1}{4\pi\varepsilon_0}$? [duplicate]

Why do we take the value of the constant in Coulomb's law as $\frac{1}{4\pi\varepsilon_0}$?
96 views

### Value of weak force coupling constant

I'm trying to get my head around the weak force coupling constant $\alpha_w$ but getting confused by different resources. Hyperphysics suggests it is tiny compared with the strong force coupling, ...
342 views

### Uncertainty of permittivity of vacuum [duplicate]

Question: The value of permittivity of vacuum, $\epsilon_0$, is given with absolutely no uncertainty in NIST Why is this the case? More details: The permeability of vacuum can be given by ...
What is the reason for some writing Faraday's Induction Law as $$\nabla \times E= -\frac{1}{c}\frac{\partial B}{\partial t}$$ versus $$\nabla \times E= -\frac{\partial B}{\partial t} ?$$
### Why are $\mu_0$ and $\epsilon_0$, which appear in electrostatics and magnetostatics, related to the speed of light which appears in electrodynamics?
$\epsilon_0$ and $\mu_0$ appear in electrostatics and magnetostatics. When we include time varying fields we have electrodynamics and the appearance of c which turns out to be related to $\epsilon_0$ ...