Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How is this possible?

  1. Jan 10, 2009 #1
    I have a quick question
    about this ananova article that's been bothering me. I can't figure out any way it makes sense. (and ananova usually doesn't publish complete bs as far as I know)
    http://www.ananova.com/news/story/sm_3148241.html
    basically, my question is: does it make sense to you? how is there voltage through a single chunk of metal? or is there something special about a burglar-proof door, like two separate panels or something? but then why wouldn't it just discharge completely when they connect a wire to the two sides?
    What am I missing?
     
  2. jcsd
  3. Jan 10, 2009 #2
    I don't think you're missing anything. I read the article three times and the source of the current is a mystery. It's pretty much a story about mysterious electrical discharge.

    How it might be possible is that there might be current leaking into some old underground pipe near the surface under the doorway from a short somewhere else in the neighborhood and he made contact with the pipe when he drove a screw down to secure the new metal doorjamb. That's as plausible a guess as any.

    It's not clear from the article if a capacitor discharge is suggested or if the current is continuous, even when the building's power was cut. Could they light that bulb continuously when the building's power was off, or was it a one-shot discharge? At any rate I assume the door has two separate 'iron' (probably actually steel) panels with lighter filler between (a potential capacitor if the two panels somehow ended up not being shorted to each other). A solid iron door would be incredibly heavy, and it would require expensive casting and then heavy duty machining to square it up.

    A more wacky notion that also occured to me is that, if the door's manufacturer included some kind of wax, or waxed paper between the two outer panels they might have inadvertently created a really big electret.

    We'll never know unless some clever detective examines the door and surroundings and figures it out and they post a follow up story.

    If we give them both a crash course in basic electricity, who will solve the mystery first, House or Monk?
     
  4. Jan 11, 2009 #3
    The story itself, from the website, sounds suspect to me.
    I would say that the whole thing is a hoax; an attention grabber.
     
  5. Mar 1, 2009 #4
    "An electrician checked the door and found it had 149 volts running through it"

    Did the electrician describe the voltage as "running through" the door? If so, I'd check his credentials.

    Even if he does mean that there was a voltage drop across the door, this article is still bogus.

    In order for there to be EMF in a chunk of a conductor, it would have to be hooked up to an external voltage source, like a battery. The door could have a charge without this, but simply having a net charge will not consistently produce 149 volts. There could be some induction going on, but that would only really work if the door were grounded and there was something else near the door that had a charge. Still, this wouldn't produce voltage across the door.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?