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13 votes

Why do charges exist in the first place?

I am going to assume that when you say "charges" you mean "electric charges" (there are some other types of charge in physics, but you probably haven't come across them). Why do ...
gandalf61's user avatar
  • 53.8k
8 votes

If there's magnetic field around current-carrying wire, why doesn't it always exist?

When we say that a current is made of moving charge carriers (like electrons), we mean that the charge carriers are moving relative to some frame. Often, that frame is "us", or more ...
Andrew's user avatar
  • 48.8k
4 votes

Why do charges exist in the first place?

Aristotle said physics is the study of change and the main way that things change is through motion. Charges, via Noether's thm, are what is required for change to occur. For example, mass is the ...
Mozibur Ullah's user avatar
3 votes

Why do charges exist in the first place?

When an electron with a negative charge and its antiparticle, the positron, with a positive charge annihilate, one possible outcome is the production of two photons. This means that it is allowable, ...
Rich's user avatar
  • 829
2 votes

How is electrostatic force 'lost' during conduction in these examples?

Charge is conserved and so if the initially uncharged glass rod has a deficit of electrons (positively charged) then the cloth will have a equal surplus of electrons. The comb becomes charged and when ...
Farcher's user avatar
  • 96.2k
2 votes

Heating a Material with Negative temperature coefficient of resistance

So, if you have thermal equilibrium, such that the rate of electrical heating is equal to the rate of convective heat loss from the resistor, the heat balance on the resistor reads $$\frac{V^2}{R}=hA(...
Chet Miller's user avatar
  • 33.6k
2 votes

What limits the size of a nuclear power generator?

To be a critical reactor, the material and geometry have to be in a balance where the number of neutrons created by fission match the number of neutrons being absorbed and leaking from the system. The ...
NuclearFission's user avatar
1 vote

Derivation and theory for $I = kV^n$

For temperatures up to a few hundred kelvin, the resistance of a metal wire is roughly proportional to its kelvin temperature, $T$, so $$R=\alpha T,\ \ \ \ \ \text{that is}\ \ \ \ \ \tfrac VI=\alpha T ...
Philip Wood's user avatar
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1 vote

About lightning and lightning conductor

Of cause, if the lightning conductor does not work properly, lightning may set your house on fire or at least set the roof on fire ore damage it. But a well build lightning conductor should work to ...
trula's user avatar
  • 6,199
1 vote

If metals can’t sustain an electric field inside them (as their electrons move to cancel it out), how do they still conduct electricity?

Well you mentioned in your question already that the electrons will be moving to cancel out an electric field. That means an electric field applied to a metal will cause a current in the metal. I am ...
Zaph's user avatar
  • 715
1 vote

Why is current through the short circuited wire not zero?

Two points on a short-circuited wire are not at the same potential—an ideal battery has a voltage difference between its terminals by definition, and that voltage difference has to be dropped ...
Rokas Veitas's user avatar
1 vote

Trouble understanding an example in electricity and magnetism by M.Purcell

Conductors, by definition, have electrons that are able to adjust themselves to any electric field present, i.e. the electrons in a conductor respond with motion whenever they encounter an electric ...
Albertus Magnus's user avatar

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