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

Phase (hot) and ground

  1. Jul 27, 2017 #1
    How exist voltage between hot and ground?
    How we are connected to ground through wood floor, building when we use tester screwdriver?
    Last edited by a moderator: Jul 27, 2017
  2. jcsd
  3. Jul 27, 2017 #2
    Hello Mark - I believe due to language issues, you question is not too clear.

    What do you mean by tester screwdriver - a voltage detector? There are different types, can you show a picture or link to the type you are thinking of?
  4. Jul 27, 2017 #3


    User Avatar
    Gold Member

    I think he means...

    Using an old fashioned neon testing screwdriver the bulb lights up when it is applied to a voltage (e.g. 240V AC). My finger on the other end of the screwdriver is not (apparently) connected to ground when I am standing on a wooden floor. So how come the bulb lights up?

  5. Jul 27, 2017 #4
    There is just enough current due to the capacitance of your body, or in the device, to light the neon lamp. Similarly the non-contact types use current into a capacitance to detect a time varying E field. These are so sensitive they can usually detect static generated by rubbing the device on your clothes.
  6. Jul 27, 2017 #5
    Where is potential difference between hot and ground?
    How we close circuit when connect hot and ground wire (I do not know path of current)?

    Same question, how circuit is closed without ground?


    Attached Files:

    Last edited by a moderator: Jul 27, 2017
  7. Jul 27, 2017 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    because the neutral is, in MOST electrical systems, grounded at the switchboard

    same answer......

  8. Jul 27, 2017 #7
    The earth and all grounded surfaces make one electrode of a capacitor - you and the instrument make up the other electrode, the air, shoes, (insulating things) make up the dielectric.

    When you open a capacitor - there is no conductor between the two terminals.
  9. Jul 27, 2017 #8
    It means that all materials conduct small current on high voltage, even clothes, floor, wall...
  10. Jul 27, 2017 #9
    "Conduct" is not the word to use here. It is how a capacitor works.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted