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Homework Help: Field strength between two wires

  1. Apr 19, 2010 #1
    I feel like a stupied girl. :(
    It think it's not very hard, but I have to have the correct answear before i send it to my school.

    1. The problem statement, all variables and given/known data

    We sometimes exposed to electric fields. To determine whether there is a risk of flashover is a rule of thumb which states that the sparks will switch if it is larger than the field strength of 1kV per mm, ie 1MV/m.

    a) How big is the largest electric field between two leaders in a 230V-power line (peak voltage is 324V)? We assume that the distance between conductors is 2mm. Reply with a rounded integer. Answear in kV/m

    b) If a person stands on a railway-wagon, an accident can happen if you come too close to the lead. If the voltage is 16kV, at which distance can a spark jump over and kill a person? The authority has a rules that says 270mm between the leaders at that voltage. Then you have gardening has objected to the management of moist air, etc.. Reply with a rounded integer.

    c) If the insulation around a conductor to a coffee machine is damaged, at what distance from the leader can get a spark to turn over to a sink? Reply with two decimal places.


    2. Relevant equations

    E=U/d


    3. The attempt at a solution

    a) 324/0.002 =162000 =162kV/m I'm pretty right here :/

    b) 16kV/1(kV/mm) = 16 mm
    16mm according to the rule of thumb 1kV per mm. I don't see how I should take the rule of 270mm into considiration. It's obvioulsy a better distans..

    c) 0.230V/1(kV/mm) = 0.23mm

    Cheers/Maria
     
  2. jcsd
  3. Apr 19, 2010 #2

    Redbelly98

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    (a) and (b) look good, though I don't understand the remark that "gardening has objected to the management of moist air, etc.." I have no idea what that means or how it enters into question (b).

    For (c), if it's a 230 V line then the peak voltage is actually 325V. Otherwise, you have the right idea.
     
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