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What about speed of electricity on a wire? Can it be added to the train's speed?

Quote from: Jack Qwek on 10/07/2016 17:01:16What about speed of electricity on a wire? Can it be added to the train's speed?Yes, if the wire is on the train then relative to the ground the electricity is speed in wire + speed of train.

Quote from: Colin2B on 11/07/2016 23:16:16Quote from: Jack Qwek on 10/07/2016 17:01:16What about speed of electricity on a wire? Can it be added to the train's speed?Yes, if the wire is on the train then relative to the ground the electricity is speed in wire + speed of train.Not if relativistic speeds are involved. No information can travel faster than c.

Let's say that at the end of a wheel there is a wire that measure electricity speed, this spinning wheel is quite big, diameter 500 meters, rpm is 100000, so the speed of this wheel will be 5236000 m/s, which is more than 1% the speed of light. So in theory, they can measure if electricity can go faster than light?

Although the flow of electricity in a wire is often referred to as the movement of electrons actually they move relatively slowly what moves fast is the electromagnetic field that is guided by the wire that moves at c.

Quote from: Jack Qwek on 12/07/2016 00:46:00Let's say that at the end of a wheel there is a wire that measure electricity speed, this spinning wheel is quite big, diameter 500 meters, rpm is 100000, so the speed of this wheel will be 5236000 m/s, which is more than 1% the speed of light. So in theory, they can measure if electricity can go faster than light?A rotating system is not an inertial frame so it is possible for one observer to measure light in another location to be faster than c, although if the observer were on the rim of the disc they would only measure it to be c. This is similar to the effect of a gravitational field.

Quote from: Colin2B on 11/07/2016 23:16:16Quote from: Jack Qwek on 10/07/2016 17:01:16What about speed of electricity on a wire? Can it be added to the train's speed?Yes, if the wire is on the train then relative to the ground the electricity is speed in wire + speed of train.I disagree but because you have been thanked 96 times I am most likely wrong.

We have to keep in mind that the speed of the electricity relative to the ground is less than the speed of light, always! If someone in the rest frame of the wire measures the speed of electricity then when transformed to the ground frame then speed will still be less than the speed of light.

For light, the speed is always the same for any observer (inside or outside the train, inside or outside the wheel, etc). But for the electricity on wire, if the observer is on the rim of the spinning disc, the speed of electricity is same as when the wheel is not spinning. If the observer is outside the wheel, the speed of electricity could be faster than c. If they do this experiment, it would be an amazing discovery.

The speed of the electron in a copper wire, which is one of the best conductors of electricity is always less than c.

it is the electrical field that travels at something like the speed of light (for typical conductor geometries, pulses travel at about 2/3 the speed of light).

The drift speed of an individual electron in a current-carrying copper wire is about equivalent to fast walking pace.

I thought it would be a good academic exercise for us to do the calculation:Let's imaging a notional conductor, a cylindrical piece of wire.Its cross-sectional area is A, the length is d and there are n charge carriers, e, moving at velocity v.Therefore the total mobile charge, Q, in the cable is given by AdneTime, t, for this charge to move along the conductor = d/vSince current, I, = Q/t we can substitute for the above:I = Adne / d/v = AvneSo v = I / AneNow i need some numbers for my notional copper wire including - number of charge carriers etc...Who would like to take up the baton...

I know that if we switch on a torch on a train, the speed of light cannot be added to that of the train. What about speed of electricity on a wire? Can it be added to the train's speed?