To get an expansion of Helmholtz energy of a) an ideal gas b) a Van der waals gas we must integrate $\left ( \frac{\delta A }{\delta V} \right )_{T}=-P$ I saw the solution is : Can you explain why is that? ....

In a physics text book I read the following: $$e/m=1.758820150(44) ×10^{11} \mathrm{C/kg} $$ In this expression, $(44)$ indicates the likely uncertainty in the last two digits, $50$. How should I understand this uncertainty? Does it mean $\pm 44$ on the last two digits? ....

If you have two parallel planes with one density of 1 C/m^2 and the other with -1 C/m^2 density and you need to find the electric field at a point in the middle, how do you use Gauss's Law? I drew a box enclosing one plane to find the electric ....

I have some trouble understanding what happens to the phase of a BEC when some particles are removed. The motivation of the question is the experiment of observing interference between two BECs. In my current picture, a BEC is a state $\Phi(r)e^{i\varphi}$, where $\Phi(r)$ is the N-fold tensorproduct of the ....

Please understand, I am not a scientist. My understanding of "nothing" is that virtual particles are constantly springing into existence on borrowed time and borrowed energy. Almost instantly annihilating each other giving back that borrowed energy. But could an event happen such as 2 antimatter particles appearing near enough to ....

For two qubits 1 and 2 with Pauli Matrices $\sigma_{x_1}, \sigma_{x_2}, \sigma_{z_1}, \sigma_{z_2}$, prove that: $$ = 0$$ I am very confused about what the question means. I thought the Pauli Matrices would be the same regardless of which qubit they belong to, which would mean that $\sigma_{x_1} \sigma_{x_2} = ....

I was wondering if liquid "air" (nitrogen, oxygen, and argon mixture) was flammable. Imagine you have a container. This container contains liquid air. The air is in liquid form, and is in direct contact with two copper rods, which when a current is ran through them, they spark. I was ....

I am trying to freshen up my memory about electrical fields and I came across this exercise from school. A sphere with a constantly distributed charge is located in between two different dielectrics (see picture at the bottom) and the task is to calculate the electrical field. I have a ....

There is plenty of evidence for a cosmological time dilation effect. For instance a supernova that takes 20 days to decay will appear to take 40 days to decay when observed at redshift $z=1$ (see Ned Wright's cosmology FAQ (http://www.astro.ucla.edu/%7Ewright/cosmology_faq.html#TD), Ned Wright on Tired Light (http://www.astro.ucla.edu/%7Ewright/tiredlit.htm)). I understand how time ....

Perhaps a question that is too naive to be on Physics.SE but I let the experts here decide (and downvote at will), but there seem to a certain company that claims to have created what it calls a "magnetic generator" where, if the machine is powered externally long enough (which ....