So, my wire just happens to contain electrons at all times but once I put a load on it the
EMF is in force and the electrons are just a conduit?
Yes. For a loose explanation - a good conducting material has a “liquid” of free electrons floating inside it, just bouncing around. When the field is applied, the electrons average movement becomes skewed toward one direction (funny enough, that direction is opposite to the direction of current as current is defined in modern physics).
Remember the atoms are packed in the wire pretty tightly. The best way to think of it is as Okrahoma mentioned above…think of a tube of marbles. You push on one end and the effect is felt at the other end almost (not quite) immediately yet the marbles themselves barely move. Kinda like a Newton’s Cradle. Here is another visualization of it: https://youtu.be/jbi7gJTPSXk?t=90
Electrons DO move in the wire just very slowly (called the Drift Velocity…as mentioned less than a millimeter per second).
Seconded. I’ve bookmarked the channel. Watched the linked video and found it fascinating, although I’ll need to view it 2 or 3 times to get the full benefit. The other vids on the channel look equally engrossing.
Of the order of speed of light in a vacuum, c.
The electric signal travels down the wire at the speed of light in the wire.
I’m reading this using lenses that work because the speed of light in the lense is different to the speed of light in air… and air being so thin, that speed is very nearly c. In fact I paid a lot to get special high refractive index lenses, 0.84, which just means I paid for a special material so that the speed of light in the material is slower… and the lense is doesn’t have to be so thick at the outside. (concave).
The correct question is then, why is the speed of electrical signal slow in wires ?
Because the fields, if they are operated by virtual photons or something else with the same property, travel at the speed of light IN THAT MATERIAL.
The speed of light in material varies because of the ratio of electric to magnetic properties of that material. It is not the old school science explanation of DENSITY. Increasing the density is one way to get more obstacles in the way, but having more atoms/ molecules that have unpaired electrons would be another. (paired for the purpose of the explanation of magnetism in materials.)
As has already been pointed out, anything with mass can’t hit c, and anything without it always travels that fast. But I don’t think that quite hits the core of your question.
Things with mass can’t move at c, but we can imagine propelling you at c if we allow for infinite energy. You’re sitting in a nice comfy chair, we add infinite momentum in the same direction to every part of your body and … In the next “instance” you are now staying still, from your own perspective, but the entire universe has flattened in your direction of travel, and time has slowed down, all the way to zero in fact.
So you’ll also instantly, from your perspective, hit whatever you’re going to hit, and transferred that infinite energy and started a chain reaction that will fry the entire universe …
To expand on this item: The preferred frame at one location, when thought of as a special relativistic inertial frame, is not the same as the preferred frame at any other location in the universe. That is, one can speak of a quasi-preferred SR frame, but every point in the universe has a different quasi-preferred SR frame. There isn’t a global one.
I’m sufficiently surprised that I’d be interested in a cite for this piece of outreach.
A follow up question then:
Why does a massless object have a position and direction of travel? If it has no mass and was not accelerated to a particular speed, then what’s the relationship to the event that spawned our particle and our particle’s eventual movement?
The way I say it is that in special relativity too there are local frames, the difference is that there is a very natural way of taking any free-falling frame and defining an equivalence class of such frames to create a global inertial frame. The difference in the cosmological case is that there is also a very natural way of creating a global frame, but only if you start with a specific class of free-falling frame.
Massless particles travel at c otherwise they don’t have energy and momentum and particle doesn’t have energy and momentum it really isn’t much of anything.
But how is it imparted?
The directionality is actually covered in Maxwell’s equations: the electrical and magnetic fields propagate in a particular direction, making up the photon.
When an atom emits a photon, the atom itself recoils in the opposite direction, and that’s another clue toward directionality.
A photon can be emitted when an electron jumps from a higher orbit to a lower one. In Newtonian terms, you’d expect the photon to be emitted in a straight line away from the nucleus, through the electron’s position. But as electrons don’t have “positions” very much, I do not know how the photon knows what direction to start travelling in.
Your question seems to be more about quantum mechanics than relativity. Even particles with mass can poof into existence without having been accelerated to a particular speed, in the classical sense. While massless particles poof into existence traveling at c, you can have a massive particle poof into existence traveling at 0.8c, say. The specific speed isn’t that interesting for your query, if I understand what you are asking.
A system that starts in some allowed configuration can change to another allowed configuration with different particle content. Energy and momentum are conserved during this change. Particle decay is probably the most straightforward example. The daughter particles aren’t brought up to speed; they are born with their speed. The directions and speeds of all the final particles are random[sup][/sup] up to the constraints of energy and momentum conservation.
[sup] “Random” doesn’t mean uniformly random, though. In general, the physical process that underlies the transition/decay/scattering/etc. determines how likely each possible final configuration is, on top of the configuration’s relative likelihood from kinematic considerations alone.[/sup]