simple electrical questions

Discussion in 'General Electronics Chat' started by yassser, Jan 29, 2013.

  1. yassser

    Thread Starter Member

    Jul 25, 2011

    there are a few things I have in mind that I can't explain .

    when someone touches a cable carrying electricity while he is wearing shoes and standing on a sandy floor , why does he get an electrical shock? , isn't sand an insulating material ? , isn't his body supposed to be floating , what is the path the current takes ?

    a similar question , why is earthing made by inserting a copper pole into the ground , what is it connected to , isn't sand an insulator?
  2. crutschow


    Mar 14, 2008
    Whether sand is an insulator depends upon how dry it is.

    And you can get a shock from a high voltage line just from the capacitance between your body and ground.

    A ground rod must penetrate the soil deep enough to contact moist soil. That's why they are usually quite long. Otherwise it would make a poor ground connection, as you might expect.
  3. Brownout

    Well-Known Member

    Jan 10, 2012
    Sometimes, you have to wet the ground ( the real ground ) around the ground rod ( the electrical ground )
  4. yassser

    Thread Starter Member

    Jul 25, 2011
    the capacitance between my body and the ground , does the ground mean the moist soil , so the first conductor is my body , the insulator is the shoes and the dry sand , the other conductor is the moist soil ? , if this is the case then I can only be shocked by ac voltages ? because capacitors are open circuit to dc voltages?
  5. yassser

    Thread Starter Member

    Jul 25, 2011
    I have another question , In a factory near by , the factor has only three cables coming from the electricity company , the three phase cables , there is no neutral cable , then they have a well at the factory with a copper rod inserted in the ground and they use it as a neutral with the 3 phase cables , is that correct? , shouldn't the neutral cable be also coming from the generator to close the circuit ?
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    It depends on the voltage. There is a reason the position to take when lightning is near is to crouch on the balls of your feet while both feet are touching, and you try to get as low to the ground as possible.

    Standing with your feet a few feet apart would allow a nearby lightning strike "ground swell" to put a few thousand volt gradient between your left foot and right foot. In that case, current would flow up one leg and down the other. A 1/2" moist insulator (foot in shoe) isn't enough to isolate you from those levels. Not all insulators are perfect.