Skip to main content
44 votes

Why don’t nuclear reactors burn through most of their fuel before discarding it?

The most important limit is that you can't separate the byproducts from the fuel without reprocessing. Among the byproducts are neutron-absorbers, which poison the desired controllable reaction. ...
BowlOfRed's user avatar
  • 40.3k
27 votes

Could you use Muons as electricity (or rather mutricity)?

You can use any charged particle to carry an electric current. We like to say that current is carried by electrons because, in metallic conductors, there is a gas of conduction electrons who are much ...
rob's user avatar
  • 90.2k
22 votes
Accepted

Could you use Muons as electricity (or rather mutricity)?

For the purposes of this answer, I'll be ignoring the fact that muons have a very short lifetime, and instead talking about how a fantasy version of a muon, one that is identical in every way to real-...
Hearth's user avatar
  • 389
18 votes
Accepted

How could one measure the capacity of a battery with one instantaneous meter reading?

Here is how. That special meter contains a load resistor, which places a load on the battery roughly equal to that of a starter motor (big load!). When the meter is clipped onto the battery terminals, ...
niels nielsen's user avatar
16 votes

Why don’t nuclear reactors burn through most of their fuel before discarding it?

The reactor core is designed with a certain amount of reserve reactivity so it can operate at full power for an extended amount of time by adjusting the control rods as the fuel is consumed and the ...
niels nielsen's user avatar
15 votes

Is electric current actually the flow of electrical charge?

electrical current is "the flow of charges" The above is true. it seems to me that electrical current is indeed caused by the electric fields along the conductor The above is true as well....
toomanyfeet's user avatar
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
  • 55.4k
10 votes

Why don’t nuclear reactors burn through most of their fuel before discarding it?

We must take a numerical example on a specific type of reactor to clearly explain the problem. PWR reactors essentially consume 235U. Natural uranium is enriched in 235U, up to 4 or 5% in uranium 235. ...
Jean Jacques's user avatar
10 votes

Flow of electrons in wire

The answer depends on the level of approximation that you are confortable with. Are we discussing a pinball like model for electrons or a quantum mechanical model? Do we consider the electrons ...
Mauricio's user avatar
  • 5,476
8 votes

How did a spark generate electromagnetic fields that radiate to places?

EM waves are generated by accelerating charges. The transmitter is a circuit that supports an oscillating current (which requires that the charges are accelerating during the oscillations). The ...
BowlOfRed's user avatar
  • 40.3k
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
  • 49.4k
7 votes
Accepted

Does the EMF of a battery change with time?

is that a result of a decrease in the EMF of a cell or an increase in the internal resistance of the cell of both? It's both. Batteries are surprisingly simple things, at least in principle. A ...
John Rennie's user avatar
7 votes
Accepted

Why electric currents in equal and opposite direction cancel each other?

In my bank account, withdrawals that are equal and opposite to deposits cancel out. Nevertheless, my account balance is not a vector. Mere cancellation of equal and opposite quantities does not imply ...
Dale's user avatar
  • 101k
7 votes

What can cause a spot above my WiFi router's antenna?

Routers produce heat which warms the surrounding air causing it to rise. This airflow carries with it any dust, aerosols, or vapours which may be deposited or condense when they hit the ceiling. The ...
David Bailey's user avatar
  • 11.4k
6 votes

Is electric current actually the flow of electrical charge?

Current is indeed the flow of electrons or other charge carriers, however, the charges flow according to the influences of the electric field experienced by the individual charge carriers (e.g. ...
Albertus Magnus's user avatar
6 votes

Is electric current actually the flow of electrical charge?

Usually, an electric current is the flow of electric charges (= electrons, ions, or positive pseudoparticles within a p-type semiconductor). However, this is not the full story. The complication is ...
cmaster - reinstate monica's user avatar
5 votes

Does the EMF of a battery change with time?

Usually, it's both EMF and (non-ohmic) resistance that change. Temperature and aging also change these. Cold cells generally have higher EMF and resistance. Old cells generally have lower EMF and ...
John Doty's user avatar
  • 21.2k
5 votes

How did a spark generate electromagnetic fields that radiate to places?

The first primitive radio transmitters were spark gaps. They generate radio waves from high voltage sparks between two conductors. The high energy excites electrons to higher energy levels where ...
Bill Alsept's user avatar
  • 4,083
5 votes

How can Electricity travel at the speed of light?

Electricity does not move at the speed of light. In a conductor the individual electron drift velocity is often surprisingly low, while the signals and energy are transmitted far faster. ...
Anders Sandberg's user avatar
5 votes

Why do electrons not remain at higher energy levels?

The short answer is that the state where the electrons are on a higher level isn't stable. Therefore the atoms in the higher energy states decay (i.e. the electrons in the atoms return to the ground ...
WillHallas's user avatar
5 votes
Accepted

Why do electrons not remain at higher energy levels?

Why don't the electrons remain in the higher energy levels? In principle, for an atom in complete isolation, the electron can remain in the higher energy level indefinitely. The higher energy level ...
hft's user avatar
  • 20.6k
5 votes

What is the "closed circuit" of a bug swatter racket?

the electric fence plate is at high voltage. the outer safety fences are at ground potential. when a bug bridges the gap established by the safety layer between the electric fence and the safety fence,...
niels nielsen's user avatar
4 votes
Accepted

Quick question regarding the meaning of Voltage of a Battery

The voltage of a battery is indeed related to the work necessary to move a unit charge from one terminal of the battery to the other. In more technical terms, it is a measure of the electric potential ...
Song of Physics's user avatar
4 votes

Why do we indicate current to be flowing against electrons in a electric circuit ? If it is a convention thenwhy do we draw it along studying it?

I believe that electric current is a kind of force The word force has a very specific meaning in physics. Electric current is not a force. A force is the phenomenon by which can objects accelerated. ...
The Photon's user avatar
  • 27.8k
4 votes

How could one measure the capacity of a battery with one instantaneous meter reading?

Typically, voltage decreases as the battery discharges, so it is probably possible to assess the remaining energy of a battery by measuring the voltage. It is also plausible that the voltage (of a ...
akhmeteli's user avatar
  • 27k
4 votes

Why is current defined as $dQ/dt$ even though it is not defined as the rate of 'change' of flow of charges?

Why is current defined as $\mathrm dQ/\mathrm dt$ [...] It isn't. Given an ideal, infinitely thin wire and a choice of which direction to call positive, the current at some point $p$ is the rate at ...
J. Murray's user avatar
  • 69.7k
4 votes
Accepted

Why are the formulae for the electric flux density and the magnetic flux density fundamentally different?

Functionally, $\mathbf{E}$ and $\mathbf{B}$ are analagous because they both represent the total field, taking into account both free and bound sources. However, mathematically, we have $\mathbf{E}\sim\...
Vincent Thacker's user avatar
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

How did a spark generate electromagnetic fields that radiate to places?

Electromagnetic fields are caused by the movement of charged particles. Modern devices use conductive antennas of a size matching a desired wavelength to emit controlled, band-limited signals of ...
Cristobol Polychronopolis's user avatar
3 votes

How does DC loses energy?

Electrons encounter a resistance as they flow through a wire. The energy used to overcome that resistance $(E=I^2R)$ is converted into heat, which is radiated in electromagnetic (infrared) radiation.
hdhondt's user avatar
  • 11k

Only top scored, non community-wiki answers of a minimum length are eligible