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A.C. current. Waving?

Tony Lockhart

Avoiding Stress, at Every Opportunity
A question I’ve had in my mind for years but am too forgetful and bone idle to ask is, how far does a ‘wave’ travel before going the other way? Should be about a 50th of how far it travels in one second?
 
Ok, thank you. So if the blue minnows stuffed into the electric string don’t travel very far, could this mean that the quality of the wiring a few metres outside the house is irrelevant, to a degree, as long as it’s doing its job? Could it explain why some of us hear a difference when trying different cables, connectors etc?
Does this mean that anyone saying that “after the electricity has travelled down miles of national grid cabling, the last few feet can’t make any difference” is missing this vital point?
 
How far they travel is obviously dependent on gauge of the conductor.
The only anywhere near logical argument about changes in cables has been that any cable can be consdered as countless L C and R units strung together randomly, and they affect how electricity (electrons) progress through a conductor.
 
Ok, thank you. So if the blue minnows stuffed into the electric string don’t travel very far, could this mean that the quality of the wiring a few metres outside the house is irrelevant, to a degree, as long as it’s doing its job? Could it explain why some of us hear a difference when trying different cables, connectors etc?
Does this mean that anyone saying that “after the electricity has travelled down miles of national grid cabling, the last few feet can’t make any difference” is missing this vital point?
I think you’re a very naughty boy.
 
So maybe simply unplugging your mains cables at both ends (wall and component) fills them back up with fresh new electrons rather than the ones that have been going backwards and forwards next to each other for years, and its these new minnows that actually make the difference rather than the ‘new’ cable itself.
 
A question I’ve had in my mind for years but am too forgetful and bone idle to ask is, how far does a ‘wave’ travel before going the other way? Should be about a 50th of how far it travels in one second?
It depends on what you mean by a wave.

Drop a stone into water and a wave spreads out, gradually losing amplitude, until it hits a discontinuity and some fraction of its energy gets reflected back - that's one type of wave. But if you float something in the path of this wave it more-or-less just bobs up and down in place - another type of wave.

In copper wire carrying mains power the electrons bob about locally, back and forward 50 times a second (60 in USA) but a remarkably small distance. However, the energy (power) is carried in an electromagnetic field along the wire at a significant fraction of the speed of light from source to load. Two different types of wave.

And the mains system is designed so that there is no appreciable reflection when the energy wave hits a load. So to all intents and purposes the wave only goes one way. A 50 Hz wave at 67% of the speed of light (to pluck a plausible number out of the air) has a wavelength of circa 4,000 kilometers. Even Land's End to John O'Groats is just 1,300 km and your power station is going to be much closer than that. So the waves do not really reflect back in a transmission-line sense - the network isn't big enough.
 


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