Friction, resistance

[goku]

does friction or resistance happen to everything, even electrons?

if so what does that mean for the future of our existance?

[UncleAl]

The world ended in 1900. The paperwork is still in process.

[Jay-qu]

one of the assuptions made in Rutherfords model for the atom is that electrons orbit the neucleus without a loss of energy - if they did well they would eventually crash into the neucleus of the atoms and be destroyed I guess :hyper:

[sanctus]

When the free electrons go through a solid they experience resistance (no friction, but if you want at microscopic level there isn't much difference). This resistance is due to shocks with the atoms (they don't actually touch them, unless they are at very high kinetic energy, but they as close until the Coulomb repulsion energy is bigger than the kinetic one and that pushes them back), the result is that they change direction. Actually this free electrons are what macroscopically we call current and the shock with the atoms is what we call electrical resistance.

[CraigD]

does friction or resistance happen to everything, even electrons?

if so what does that mean for the future of our existance?

If you’re asking “will an electrons in an atoms lose kinetic energy and eventually collide with a proton in the atom’s nucleus to create a neutron, the answer according to current widely accepted theory is no. Due to their small size relative to their quantum wave function wavelength, they are effectively “locked in” their orbits, capable of changing orbits only in discrete “jumps”, or transitions, and never below an absolutely defined lowest orbit

 

As Jay-qu notes, early modern theories, (like those by Rutherford ca 1911) of atomic structure simply assumed this, in order to make the theory agree with observed reality (eg: atomic matter seems pretty stable). By 1913, Bohr and others had taken the 1900 and 1905 theories of black body emission of light and the photoelectric effect, and constructed a compelling theoretical explanation of this. For the next few decades, these old guys and a new generation of folk like Pauli and Heisenberg developed these theories into the now famous standard model of particle physics, with detours to perform spectacular stunts like providing the engineering details for the construction of atomic bombs, transmuting lead into gold, etc. Along the way, they got the theories to agree with Relativity. Nearly all of the top folk (who, like rock stars, nearly all knew each other and hung out together) wound up getting Nobel prizes and other accolades.

 

A good, brief description of the history and theory relevant to your question can be found at the wikipedia article “Bohr model”

 

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As sanctus notes, outside of their “locked in” orbits in atoms, electrons are a whole different story, transferring energy in all sorts of ways one could term “friction, resistance”.

 

Though I’m pretty sure everyone here has a solid understanding of conservation of energy, I think it’s wise to agree on a good working definition of the term “friction”. Friction is a force that results in work (transferring energy) in a mechanical system other than the main or desired kind. All that distinguishes it from any other work is our subjective “dislike” of it, not any fundamental uniqueness in the forces (bosons, in particle physics terms) involved in it.

[Qfwfq]

All that distinguishes it from any other work is our subjective “dislike” of it, not any fundamental uniqueness in the forces (bosons, in particle physics terms) involved in it.

I loath cold and I just love heat. I would hardly call any forces "friction", to me there is simply no such thing as friction. :hyper:

 

The most appropriate distinction is that of dissipation into thermal energy, or chaotic motion of many bodies. For a single electron one could hardly talk about friction until you shoot it through a hadron or an atomic nucleus.

[HydrogenBond]

Friction might be loosely defined as a decrease in total kinetic energy or momentum due to the irreversile loss/change of energy into heat. In the case of electrons, they will lower momentum when they fall into lower orbits and give off heat, but once they find a stable position, there either appears to be no friction or else background energy is constantly compensating the friction. At near absolute zero electrons still have momentum implying a ground state where friction ends or a place where experiments end, since there is still background energy close to absolute zero. The period of electrons between low potential energy or more monentum near the nucleus and high potential energy or less momentum away from the nucleus seems to reflect them without friction only, changing between other states of energy that is not heat. However backgound energy is still there and constantly should add to their potential energy keeping them in an excited state unless friction loss balances energy input.

[Jay-qu]

In the case of electrons, they will lower momentum when they fall into lower orbits and give off heat, but once they find a stable position, there either appears to be no friction or else background energy is constantly compensating the friction.

 

More specifically the electrons will emit a photon of energy equal to the difference in the energy levels it changes between. They dont 'find' a stable position they have allowed orbits that satisfy the equation 2*Pi*r = nLambda (n = 1,2,3...) ie the circumference of the orbit must be a whole number multiple of the de Broglie wavelength of the electron.

Something else interesting to note is that the electrons cannot be directly obsered 'jumping'. Sort of like the watch kettle never boils, our observation prevents the electron from jumping and the moment you 'look' away when you look back it will be in the other position :hyper:

[CraigD]

I loath cold and I just love heat. I would hardly call any forces "friction", to me there is simply no such thing as friction. :hyper:

 

The most appropriate distinction is that of dissipation into thermal energy, or chaotic motion of many bodies. For a single electron one could hardly talk about friction until you shoot it through a hadron or an atomic nucleus.

I believe you’re right, I’m wrong, on the correct usage of the word “friction”, which non-technically means “rubbing”. Perhaps I should have used a more general term, such as “drag”, or “energy loss”.

 

The point I was attempting to make is that, unlike fundamental mechanical terms like mass, distance, time, force, and work, which objectively describe a mechanical system, drag is a subjective term, requiring some information about what the system is intended to do. For example, loss of kinetic energy by a charged particle that induces a current passing through a magnetic field might be considered “drag” if the effect is undesired, or “transfer of energy” if it desired.

 

Upon reflection, I think my point is rather weak. :hihi:

[goku]

perpetual motion? is that what your saying?

a never ending energy that keeps the electron in motion, but does not over accelerate it.

???????

[CraigD]

perpetual motion? is that what your saying?

a never ending energy that keeps the electron in motion, but does not over accelerate it.

???????

In a sense, you could say that. However, you can only add, not take, energy from an atom with its electrons in their lowest energy state, so it’s not a useful “perpetual motion machine” like the ones some fringy folk claim to have.

 

Also, recall that, by plain old centuries-old Newtonian mechanics, objects in motion don’t require an external force to remain in motion. Even before introducing quantum mechanics to the modern description of the atom, folk were comfortable with the idea that electrons could remain in circular motion without the intervention of external forces.

 

It’s really not wise to think of atoms as classical systems, like miniature moons orbiting a planet. Quantum effects so dominate things on this scale - Jay-qu’s post #8 notes a few of the weird consequences of this – that visualizing it as analogous to the macroscopic objects we’re intuitively familiar with is more confusing than helpful. For example, it’s practically impossible to explain the characteristics of a LASER without thinking of its atoms in a quantum mechanical way.

[sanctus]

In a sense, you could say that. However, you can only add, not take, energy from an atom with its electrons in their lowest energy state, so it’s not a useful “perpetual motion machine” like the ones some fringy folk claim to have.

 

i don't really agrre with you CraigD, to me the electron is in no motion, it is still and when measured it shows itself where the wave function dictates.

[Qfwfq]

i don't really agrre with you CraigD, to me the electron is in no motion, it is still and when measured it shows itself where the wave function dictates.

:hyper:

 

When you measure the position you find it in some position but there is also a distribution of momentum, kinetic energy and orbital angular momentum. Actually, for its momentum distribution to be concentrated in zero the position distribution would have to be flat.

 

If it isn't in an eigenstate of v = 0, it makes no sense to say it is still. It does make sense to say it's in a steady or "stationary" state if it's an eigenstate of the hamiltonian, but that's a different matter from saying that the orbiting electron "doesn't move".

[HydrogenBond]

A body in motion will continue in motion unless acted on by a force. The electron in motion is acted on by electromagnetic force stemming from the nucleus. It should be decaying or decellerating unless countering energy is being pumped into it. Orbital transitions are quantum but within a stable orbitial there is a spectrum of kinetic and potential energy combinations. The wave function accommodates this range. External input comes from electron decel throughout the universe, i.e, background radiation within the tiny increments needed to perpetuate motion. This might be very long wavelength energy. Stars and nuclear fusion create new atoms all the time and keep the energy needed to counter decay coming. This point of view is contrary to current thinking because science often needs to isolate phenomena in a box to help narrow what we are looking at. It often forgets that the animal in the cage is not the animal in the jungle.

[sanctus]

Yes you both are right.

 

Question: Hydrogenond are you saying that the extra energy that the electron looses due to acceleration is compensated by background radiation? Just to be sure I understood you right.

[CraigD]

Here’s my understanding of the fundamental interactions in a hydrogen atom:

quarks (fermions, exactly 3 of them) in proton emits photons (bosons) of magnetic force; electron (also a fermion) emits photon of magnetic; electron absorbs photons from quarks, quarks absorb photons from electrons; Quarks emit and absorb gluon, W, and Z bosons.

 

In a universe consisting of more than a single hydrogen atom, the electrons. The electron and the 3 quarks interact with fermions other than themselves via photons of magnetic force, and electrons interact with photons other than those emitted by the quarks, of many wavelengths, but none of these external interactions are necessary for the atom to remain in its stable, lowest energy state.

 

So I disagree with Hydrogenbond’s assertion that the stability of atoms require tiny interactions with external “background radiation” photons. The electron is free to interact with such radiation, but doesn’t require it to retain the quantum wave function that defines it in orbit around the nucleus.

[Qfwfq]

I also disagree with Hydro and I'll add that, after the results of Rutherford, a stable ground state needed to be somehow explained because the orbital motion implies acceleration and, according to classical electromagnetism, an accelerated charge will radiate electromagnetic energy. QM provided the first answer and field theory can refine it with the mutual force seen as an exchange of virtual photons between the two, without the need of photons from outside compensating any loss.

 

Hydro, according to your depiction, if countering energy is needing to be pumped in from outside, where would the lost energy be going?

 

According to the notion of potentia, which Heisenberg favoured like I also do, the electron is "potentially" following no end of possible trajectories around the nucleus. As long as there isn't an interaction that involves a "smaller" set of these potentialities, the electron-nucleus system will be "moving" according to coherent contibutions from the set of all of them. When the contributions are all of the same Hamiltonian eigenvalue the overall result is a steady state.