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I'm wondering how exactly voltages are transfer between wires. I mean, once I've a voltage lets say 5v and I pulls from it a "wire" (not resistor) then at the end of the "dangling" wire itself the voltage is 5V and I know why! but I ask how exactly 5v transfer to the wire to be the voltage at the end of the wire 5v?! is it taking time while transfer from voltage source to the end of the wire?!

for example lets say I have voltage source(5v) and I pulls from it a dangling wire, so at the dangling wire the voltage is 5v, is it take time from the voltage source 5v to be transferred to the dangling wire to be 5v?! I mean once we connected dangling wire to the source of 5v, is it taking time from the the time that I connected "dangling wire" to voltage source(5v) to be 5v at the wire?

thanks in advance.

Ryan
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    I think you need to do some major research into electronics. First of all, you don't have 5V anywhere. Voltage is not a thing to exist, it is a difference between two points. That is what makes a voltage. – Puffafish Jan 17 '19 at 13:29

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Yes, it takes a little time, but it's very fast -- nearly the speed of light. So if you have a 6-inch piece of wire, the voltage will appear at the far end within 1 ns.

Dave Tweed
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  • So I can Imagine it "implicitly" like I'm charging a Capacitor but it takes time around zero to be charged..ye?! – Ryan Jan 17 '19 at 13:14
  • More information at this earlier question: https://electronics.stackexchange.com/questions/414595/a-question-about-electrons-charges-and-current/414602#414602 – Peter Smith Jan 17 '19 at 13:17
  • Inside the tiny computers used in laptops, desktops, smartphomes etc, the patterns of wiring are so thin and narrow that the wiring resistance sets the limitation of computer speed. The electric fields, which change as the voltages change, store energy. Your voltage source needs a little time to provide that energy; the measure of current is the measure of how fast the electric fields can be changed, and thus is a measure of how fast the changes, the signals, can spread around the silicon *AND* how fast the chip can communication (with bits and bytes) offchip. – analogsystemsrf Jan 17 '19 at 13:20
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    Actually, it's the measure of **voltage** that measures how fast the electric fields can be changed. Also, in some circuits the speed is limited by the drive current of the transistors rather than the wiring between them...sometimes the wiring itself limits speed, sometimes the transistors do. – Elliot Alderson Jan 17 '19 at 13:42
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It does take some time, yes, but the speed is so fast, that you can neglect it in many cases. High-speed electronics on the other hand have to deal with this issue.

The propagation speed of your signal depends on some properties of your cable, namely capacitance (C) and inductance (L). The wikipedia article for "Velocity factor" gives you a table with some examples for different types of cables and there propagation speed. You will see that the slowest speed is still more then 50% of the speed of light, so the 5V singal of your example will travel with at least 150,000 km/s. Or in other words: The signal passes a cable with a lenght of 1m in 6,7 nanoseconds.

jusaca
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  • thank you for your question .. if you don't mind I would like to ask two questions and there's no need for thread to be created for them. why musn't I connect different voltages in parallel? also actually why I can connect them in parallel if they are "equal" .. why is that correct? Second question, why in digital logic for determining what's the function of any circuit it's sufficient to to find all the possibilities that leads to output =1 and since we create the function? is it because if we don't have "1" then it's definite 0 then the same function satisfied ? thanks in advance. – Ryan Jan 17 '19 at 14:40
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    Well, that is a lot to explain for this thread. – jusaca Jan 17 '19 at 15:52
  • You can think of a voltage or electrical potential as a level of water. If you connect two containers with different water levels then there will be a flow of water to equalize the levels. It is similar with voltage sources, if they have different levels there will always be a current flowing between them to cancel out the potential difference, while the voltage sources itself are trying to keep the potentials stable. This creates unnecessary currents and loads your supply. You don't have this problem if your voltage sources have the same voltage to begin with. – jusaca Jan 17 '19 at 15:58