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Puzzle. Electrical VS solid bar switch.

  1. Jan 13, 2016 #1
    Good Evening,

    I am not a science "professional" nor even a Physics Graduate. I am, however, interested in anything with a science twist. I have created an account on this forum hoping that someone can answer my puzzing question...

    Start with the simplest circuit. Battery, switch, two wires and a bulb.
    Switch on and the lamp lights.
    For this puzzle, assume NO resistance in the wire and a bulb (LED or whatever) that has no resistance (so, to all appearances it lights istantly).

    I realise that electron flow is slow 0.02cm / second?
    However, effectively the speed of electricty is c (speed of light) or very near c.
    So, if the wires were 186,000 miles long there would be a delay of 1 second between switch ON and light ON.
    Additionally, a 1 second delay between switch OFF and light OFF.

    If the wires were 1,860,000 miles long there would be a 10 second delay.
    (all theoretical, of course. Hence assume NO resistance in the wires etc).

    Now the puzzle:
    In the circuit the wires are only 1cm long.
    But... the entire circuit is 1,860,000 miles away.
    There is a bar 1,860,000 miles long - this bar can be used to press the switch ON.
    From 1,860,000 miles away you press the end of the bar.
    The other end of the bar presses the switch ON.
    The light comes on instantly.
    NO 10 second delay...

    Have we just transmitted a signal TEN times faster than the speed of light?

    I think the line now is, "discuss"...

    Hoping you can help and/or gives you all something to chat about over a beer or two.
  2. jcsd
  3. Jan 13, 2016 #2


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    Nope. The 'press'ure propagates throug the bar with the speed of sound.
  4. Jan 13, 2016 #3


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    Interesting! But there are some thinhs I did not understand. How is the bar placed? Sorry I can't visualize. Wouldn't two such bars be needed(one in forward path and one in return path of the current)?
    A diagram would be helpful.
  5. Jan 13, 2016 #4
    Ah ha, thank you BvU !
    So, if the bar was 650 miles long (again, in space, no weight etc) and I moved one end 20cm, it would take an hour before the other end moved 20cm?

    Only one bar - used to press the switch, and the switch is now 1,860,000 miles away. Imagine having a finger 1,860,000 miles long to press the switch.

    Apologies, I have to go out. I'll check in here tomorrow.
  6. Jan 13, 2016 #5
    Done some more research - cheers BvU, answered my puzzle completey!!

    I'm off to see Star Wars :)
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