# Tag Info

2

There is no such thing as perfectly non-conducting. We just simplify things into conductors and insulators. A current will flow from the plastic comb through you to ground, just not as quickly as it would from a metal object connected by a copper wire. The comb can pick up paper because the paper isn't a good conductor. The electric field from the charged ...

1

The field would, strangely enough, be equal to that of a uniformly charged sphere of charge $q$. The placement and shape of the cavity doesn't change the field outside the sphere. By using Gauss's law, we see that $$\oint \mathbf E \cdot d \mathbf a = \frac{Q_{enc}}{\epsilon _0}$$ Where $Q_{enc} = q -q +q = q$ The point charge in the cavity will induce ...

6

Elementary particles have quantum mechanical spin. This induces a spin magnetic moment, independent of the presence (or, indeed, absence) of a (net) electric charge. This is how the neutron attains its magnetic moment (as you already mentioned). The case of the neutrino magnetic moment is slightly confusing, as they are not completely understood yet. ...

0

As the hair have negative charge it get attracted to the positive charge of the comb. When we take comb to the bits of paper then it get induced

4

The charge is distributed uniformly on a spherical surface, but that is a function of the high degree of symmetry on the situation. In general the charge tends to accumulate most strongly near pointy bits and most weakly in depressions in the surface. There are several way to understand this. My favorite is not necessarily the most helpful for a beginner, ...

3

Actually the framework where one can describe electromagnetic fields is a classical framework. When one is talking of photons phonons etc one is in the quantum mechanical regime where the concept field, is different. A classical field in physics: A field can be classified as a scalar field, a vector field, a spinor field or a tensor field according ...

0

The entropy can be written as (discrete form)$$S=\sum_i p_ilog(p_i)$$ So you must identify what the uncertainty in your problem comes from, you would think that you have (in principle) exact deterministic equations for the evolution of these particles, so there is no uncertainty with respect to that. If you have unknown initial conditions then you could ...

0

I'll make this an answer, even though it is more of a drawn out comment. As I mentioned as a comment, computing the potential energy is trivial. If you want speed, you'll probably want to look at fast methods for long-range interactions. The link takes you to state-of-the-art libraries and methods, but any introductory book on computational statistical ...

0

Correct me if I am wrong, but a potential energy can only be determined for a conservative force field, which means that the force can only depend on position. So, because the charges vary with time you can not determine the potential energy. If the velocity is small compared to the oscillation, such that the displacement during the common period of the ...

0

There is no charge anywhere in the charged black hole solutions (the divergence of the electric field is zero everywhere). Gauss's law applied to any surface enclosing the singularity will tell you that all of the charge is inside that surface. However the singularity itself is not part of the spacetime. There are two ways of looking at this. You can say ...

1

Depending on how you feel philosophically about these things, either on the horizon or at the central singularity.

Top 50 recent answers are included