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Author Topic: Can normal household current flow without wires between two terminals?  (Read 7412 times)

abhishek

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abhi asked the Naked Scientists:

Can normal household current flow without wires between two terminals?

What do you think?


 

Offline Soul Surfer

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In general no. There must be a conducting path between the terminals and this is normally provided by wires of various types but other materials could supply a conducting path.   

240 volt AC mains will jump across a small air gap of around a millimetere.
If the air is ionised and at a low pressure current will flow acrosss much larger gaps like flourescent tubes but there needs to be a high voltage pulse or some other device to initially ionise the air. Most aqueous solutions including tap water and the human body also conduct electricity well enough for a significant current to flow. this is why electricity in wet areas is so dangerous.
 

Offline RD

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If the insulation on the wires is poor, (e.g. perished rubber), and wires are damp,
then household current could flow without the metal conductors touching. (old house scenario).
« Last Edit: 03/08/2008 01:08:53 by RD »
 

Offline LeeE

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I believe that because air is not a perfect insulator, there is a very tiny and negligible flow of current.  The build-up of ordinary house-hold 'grime' across surfaces can also provide a very low conductance path too, but once again, any current that flows is tiny.  Mitigating against these factors is the oxidization of any bare conductor surfaces, which insulates them - in the UK type of mains socket, inserting and removing the plug wipes the conductor surfaces clean of the oxidization (this applies to and works for most types of electrical plug/socket, so when you get an intermittent fault in something electronic e.g. Hi-Fi etc, it can be worth just breaking and then re-making the connections).
 

lyner

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It all depends on what you mean by your question. You won't get enough current to run any 'mains - operated' device to work because the path resistance would be too high.
However, if you are talking of safety, it is more than possible for a path between two terminals (or, more likely, between the live terminal and Earth) to let enouch current through to give an electric shock. Contact with a wet tabletop on which an electric kettle lead is resting could provide a path from one hand  through you to a hand resting on the metal case of a cooker, for instance, could allow  40  to 50 milliamps to pass. That could kill you after a relatively  short time.
 

Offline graham.d

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To be a little pedantic, there will be some current flow because the source is AC and there will be capacitance between the wires. There will also be some power dissipated in the finite resistance of the wires as a result. I don't think anyone should be too worried about the resulting electricity bill from this though :-)
 

Offline syhprum

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Depending on the spacing on the terminals there will also be some radiation of the 6000 km wavelength power but this also will have little affect on the power bill.
 

lyner

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This one is a real TNS special, ain't it?
 

Offline chris

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This one is a real TNS special, ain't it?

pardon?
 

lyner

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An ambiguous question, followed by  random answers  about all sorts of things.
 

Offline LeeE

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Tee hee :D
 

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