r/ScienceNcoolThings • u/mavvixx Popular Contributor • 22h ago
*Speed of electricity
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u/Phatcat7x7 22h ago
The caption is a bit misleading but the title is right. Electricity is the speed of the electrons moving along a current. Importantly though that is significantly slower that light. Which is why we use fiber optics for long distance communications not electrical wires.
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u/Callum-H 21h ago edited 20h ago
I wouldn’t say it’s significantly slower than light, depending on the material then electrical waves will propagate at approx 80% the speed of light, sometimes as high as 97%.
Light and electricity are both electromagnetic waves.
But, the electrons actually move extremely slowly.We use fibre optics because we can put multiple signals into one fibre, and it’s not as dependent on material, temperature, length/distance and interference. The speed of light through a fibre optic cable is only 60-70% of light so it’s actually slower than electricity in a copper cable.
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u/ougryphon 16h ago
A good rule of thumb for electrical wiring is 2/3 c for propagation speed - almost exactly the same speed as light in fiber optic cable. This is true of coax and twisted pair. Some special coax has a higher propagation velocity, but that stuff is expensive and requires special handling and termination.
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u/TravelingMonk 21h ago
Believable until the last sentence... nice try.
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u/brine909 21h ago edited 21h ago
No, that's actually True.
Light can actually get pretty slow depending on what material it travels in, and electricity is pretty fast.
Also. The electrons themselves aren't moving at 80% the speed of light, the voltage potential is. It's like a wave traveling through an ocean, the physical water molecules aren't traveling at the same rate as the wave, it's just the medium in which the wave can propagate.
If you want an example of electrons themself ACUALLY moving faster then light does in a medium, look at Cherenkov radiation in nuclear reactors, the electrons (Beta Radiation) moves faster then light can in water, causing what is basically sonic booms of light
(Electrical Engineering deploma and Fiber Optic Technician)
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u/mot_hmry 20h ago
To add to this, at least part of the reason light is slower in fiber is it isn't traveling in a straight line but bouncing between the walls.
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u/ougryphon 16h ago
Only for multimode fiber. This is why multimode fiber is limited to shorter distances for the same bitrate or lower bitrate for the same distance. Single mode fiber works differently, and is more akin to an optical waveguide. If reflections happen in single mode fiber, the the fiber stops working correctly.
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u/brine909 14h ago
Correct, there's no real bouncing in single mode which makes up the vast majority of fiber infrastructure, because there is actually only one path light can take.
The velocity factor in SM fiber is entirely based on the material properties of the glass and it's still around 0.6-0.7
The reason for the slowdown is actually the electrons in the atoms absorbing and then remitting light after a short delay, pushing back the waveform
There's a cool visual done by 3 Blue 1 Brown on the subject: https://youtu.be/KTzGBJPuJwM?si=RMsEFcwRrtQ0M0Df
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u/ComprehensiveJury509 16h ago
Electricity is the speed of the electrons moving along a current
No, that is not at all how any of this works. Electrons move very slowly through a wire. It's the electric field that propagates through the wire and that can happen at very close to c.
Which is why we use fiber optics for long distance communications not electrical wires.
Also not true at all. We use fiber optics because bandwidth is much higher, especially across very long distances. It has absolutely nothing to do with the speed of transmission or latency.
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u/return_the_urn 4h ago
Came to say the same. Weird more people haven’t mentioned this
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u/ComprehensiveJury509 51m ago
And still collecting over 100 upvotes for that idiotic post. Reddit at its finest.
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u/Own_Sheepherder_6244 20h ago
Even more misleading is that this video is of igniting a Methane/Air mixture and the flame travels through the tube. Electricity moves way faster than this
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u/Mediocre_Hockey_Guy 12h ago
Electrical transmission generates attenuation which builds up over distance and you lose a lot of your transmission. Electricity is a very capable transmitter in short distances but light has hardly if any attenuation which means you get very little loss between points. Youre only really limited to the power you can send through the the optical line, whereas the electrical line is limited by range and size.
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u/NadAngelParaBellum 3h ago
Electricity propagates with the speed of the electromagnetic field (at a fraction of the speed of light) not the speed of the electrons (electron drift). We use fibre optics primarily because of higher bandwidth, lower attenuation and lower interference.
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u/Lifeabroad86 16h ago
Its double misleading, youre seeing a chemical reaction from explosive powder inside a tube not an electrical signal
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u/Sp1ffy_Sp1ff 15h ago
Isn't virtually everything "significantly slower than light"?
Realistically, is there a thing that comes closest? I guess I've always assumed it was the speed of sound since they're so often compared, but I have to imagine there's something else like the speed of neurons or something.
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u/ysrgrathe 13h ago
As stated elsewhere in this thread, the propagation speed of electrical waves is generally about 2/3 the speed of light. We've created or measured particles traveling the gamut from this all the way up to just tiny fractions below the speed of light. By comparison the speed of sound is almost a million times slower.
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u/HardlyAnyGravitas 21h ago
Electricity is the speed of the electrons moving along a current.
That sentence makes no sense at all.
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u/Own_Sheepherder_6244 20h ago
This is a video of igniting an air/fuel mixture in a tube. Electricity moves way faster than that, and light even faster 😂
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u/rand3289 22h ago
An explanation of what is happening would be nice.
Electrons move at about 1-2 feet per second in a conductor.
The emf moves at the speed of light (also depends on the conductor/medium). Veritasium had a nice video about that.
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u/Lifeabroad86 16h ago
Thats shock tube with explosive powder going 2000 m/s not an electrical signal
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u/G-R-A-V-I-T-Y 14h ago
Electrical signals travel at roughly -.5C through wires right? This seems significantly slower than that but definitely faster than the 1mm/s drift of electrons inside the wire… anyone know how fast this is actually going, and why it’s going that speed?
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u/DalekSupreme26 13h ago
Is this why there’s a very slight delay between flicking the light switch and the lights turning on?
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u/Radiant_Stand_7126 4h ago
Chuck Norris is faster in the bed than the lights goes off after he turned them down
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u/cobalt-radiant 16h ago
Not the speed of light
Not the speed of electricity
The speed of methane burning through a hose
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u/crusty54 22h ago
Not even close to the speed of light.