# Tag Info

• 39.3k

### Local gauge transformations and Noether Current

A global/$n$-parameter quasisymmetry is the realm of Noether's 1st theorem. Example: Global gauge symmetry in E&M with matter sectors implies electric charge conservation, cf. e.g. this Phys.SE ...
• 170k
Accepted

### What does it mean to give the fields energy and momentum?

Fields can exert forces on charged particles. Force by definition is the rate at which momentum changes. Meaning when the field exerts a force on charged particles it increases its momentum, this ...
• 4,471

### Why is thermal noise Gaussian distributed in voltage, but Rayleigh distributed in amplitude?

The amplitude is $\rho^2=x^2+y^2$, which is by definition positive, and which will obey Reyleigh distribution, if $x,y$ are a bivariate normal. Note also that detector is always a quadratic detector - ...
• 39.3k
Accepted

### On the motion of a charged particle in a magnetic field

Yes indeed particles oscillate around their equilibrium trajectory in a particle accelerator. The emitted radiation is due to the circular orbit itself and is named the synchrotron radiation. What you ...

### Magnetic potential in spherical coordinates

$\nabla\cdot{\bf B}$ does not equal zero for the $l=0$ term. $\nabla\cdot{\bf B}=4\pi\delta({\bf r}$) (in Gaussian units).\
• 1,135
Accepted

### Magnetic potential in spherical coordinates

The equations $\nabla \cdot {\bf B}=0$ and $\nabla \times {\bf B}=0$ imply that ${\bf B}$ can be written as the gradient of a scalar potential $V$ satisfying Laplace's equation in the current-free ...
• 23.6k
1 vote
Accepted

• 38.4k
1 vote

### UV Wavelengths Sparkd

When you have a spark in air you get an emission spectrum that will look something like this. So you see a emission from the nitrogen and oxygen atoms. You can see that there is some UV from in the ...
• 1,004

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