Why is it that currents don't flow at the speed of light, but rather significant ratios of the speed of light. I don't have any formal reasoning as to why they would flow at the speed of light-I just feel as if it would make sense. That being said, the fact that they do move at near the speed of light is also peculiar to me. Lastly, if you have current and area determined, can you figure out the velocity of the charges? I suppose you would also need to know how big the charges are. I just have no intuition as to how to go about analyzing the speed of current in some given wire.
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A current is nothing more than charged particles moving. Since those charged particles also have a mass, it follows that they cannot possibly reach the speed of light.
In a real material that conducts electricity, the average net velocity of charges is actually very, very low, because they bump into atoms all the time, which basically sends them flying off in random directions until they get acellerated again.
The key word that you'd be interested in is drift velocity.
EDIT: However, something is quite fast (almost speed of light), and that's the propagation of the electric field associated with the current (see comments).
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From above (EDIT: However, something is quite fast (almost speed of light), and that's the propagation of the electric field associated with the current (see comments).)
Any signal traveling down a twisted pair or a coaxial cable for example is known as a TEM wave (Transverse Electromagnetic) Called the Poynting vector it has an E Electric field and an H magnetic field which are both at right angles to the direction of flow. This signal could be a step or a sine wave travels at the speed of light based upon the medium between the conductors.
So called electron flow or current therefore cannot be the cause of the magnetic or Hi field. We know electrons flow slowly with a drift velocity. We must conclude therefore that the electric current is a secondary effect from the primary energy (Energy Current) flowing in the space. Much like trees wafting along the road when a car passes by. Also if a signal travels at the speed of light for the medium what is going on with the +ve conductor and this electron flow. Conventional theory has electrons flowing back to the source as in electrons flow from -ve to +ve. That means I have electrons drifting back towards the signal source positive terminal yet magically creating a magnetic field traveling towards the load at the speed of light. I think not!
Malcolm F
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Current is movement of charge. In conductors that's usually electrons doing the movement (flowing). One of the things keeping them from moving quickly is that they bump into each other and all the metal atom nucleus's constantly. Secondly, because your battery isn't sufficient, it creates a very limited potential difference. Even if the electrons never bumped into any nucleus, by energy conservation $\frac{mv^2}{2} = eV$ the electron speed $v$ will be much less than the $V$ potential, compared to the speed of light. Also, then there'll be other relativistic effects. relativistic effect means , that as you will move faster , it will require more energy to further increase your speed . If you take a very high potential Battery .
In the case of an induced EMF circuit , however, this energy conservation relation won't hold as now $\vec E$ / $\vec B$ aren't conservative , so , here relativistic effects and resistance only will be the reason why current can never attain speed of light .