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I was looking up the difference of the speed of electricity versus the speed of light online and I found that the speed of electricity can approach (up to 90% of) the speed of light at 186,000 miles per second or approximately 300,000 kilometers per second. But, the comparison that I saw was with light traveling in a vacuum versus electricity traveling via a medium such as a cable. So, my question is what would be the speed of electricity in an absolute vacuum? Please help me understand.

Qmechanic
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Michael Kleemoff
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  • When you refer to "electricity" you probably mean electrons, no? Have a look at accelerators, which in the simplest case is called a cyclotron. If you have enough energy and long straight line, the electrons can reach any speed as close to the speed of light as you like them to. However, no matter how much energy you put into them, they won't reach the speed of light. See https://physics.stackexchange.com/q/1557/ – Semoi Dec 14 '19 at 19:41
  • @Semoi Thank you for answering my question. I will continue my studies to increase my knowledge and understanding further in this area. – Michael Kleemoff Dec 14 '19 at 20:49

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Remember that light is made of photons with no mass, so by definition they travel at the speed of light in a vacuum.

Electricity is electrons flowing through a wire, electrons do have mass, so they cannot ever travel at the speed of light, even in a vacuum.

The question "how fast do electrons travel in a vacuum" is like asking how long is a piece of string, it just depends how much you accelerate it, the only catch is that it must always be less than the speed of light.

Charlie
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  • But, I suppose that there's a set potential difference at which electrons will flow through a vacuum gap (space between two charged plates, for example). Knowing this potential difference, cant we calculate the speed electrons will reach? – corcholatacolormarengo Dec 14 '19 at 20:16
  • In theory yes, if you know the kinetic energy that the potential gives each electron you could calculate the velocity from $K_{E}=\frac{1}{2}mv^2$. – Charlie Dec 14 '19 at 21:59
  • The "speed of electricity" can only mean the speed of the electrical field, hence if light. In vacuum it is "c". This speed should not be confused with the speed of charge carriers. – my2cts Dec 15 '19 at 09:26