Physics Help Forum Is this a circuit?

 Electricity and Magnetism Electricity and Magnetism Physics Help Forum

 Oct 20th 2017, 05:00 AM #1 Senior Member   Join Date: Feb 2017 Posts: 141 Is this a circuit? I saw on television that a man was repairing something and he touched a live wire and so he got a shock. Now next was a man wearing rubber slippers, so this man also touched a live wire but got no shock. Next was a man who wore rubber slippers but kneeled down and he got a shock. So in this episode they explained that In first case the circuit was complete so current flowed through this persons body. This circuit contained live wire, a person, and the floor. In the second case the circuit was broken because of the rubber slippers so this person did not get a shock. In the last case the person kneeled down so his body was in contact with the live wire and the floor so the circuit was complete here and this person got a shock even though he wore rubber slippers (Rubber is a bad conductor of electricity and i think it is also an insulator). So can a live wire, a person and the floor constitute a circuit? Also tell me what is a circuit. I think a circuit is where there is a circular flow of electricity. But in the above case if it has to be a circuit the current flowing through a persons body and to the floor should return to the live wire. But i don't think that happens so how can this be a circuit? Last edited by avito009; Oct 20th 2017 at 05:14 AM.
 Oct 20th 2017, 06:05 AM #2 Senior Member   Join Date: Apr 2017 Posts: 154 Mains supply is alternating , the two wires coming from the company change from +ve to -ve 60 or 50 times a second ... there would be no difference between the two wires , except that one is connected to earth at the power station ... this wire is called neutral , and you can touch it and not get a shock because it's at the same potential as earth .. But when the live wire is connected , either to neutral , or earth, then a current flows , if you are between earth and live the current flows through you .... how much will depend on how well you are connected to earth ... feet in a puddle of water perhaps enough to kill you .... feet on a wooden floor you may not feel it since wood is a good insulator ... Circuit breakers eliminate the risk of electric shock , they detect if there is more flowing in the live wire , compared to the neutral , if there is then some must be going through the earth and something is wrong and the breaker switches off the power , before this builds to a dangerous level. Last edited by oz93666; Oct 21st 2017 at 06:35 AM.
 Oct 21st 2017, 04:58 AM #3 Senior Member   Join Date: Feb 2017 Posts: 141 More Clarity. That does not answer my question. My question is that: Is the live wire, the person touching the live wire, and the floor a circuit? Also tell me whether it is a parallel circuit or a series circuit?
 Oct 21st 2017, 06:34 AM #4 Senior Member   Join Date: Apr 2017 Posts: 154 It's a series circuit ..... It starts at the live wire , next the fingers touching the live wire , through the body , out through the feet into the ground , through the ground many Km through the ground and out through an earth connection into the generator at the power station.
Oct 21st 2017, 06:52 AM   #5
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 I think a circuit is where there is a circular flow of electricity
This is a common misconception. It is not true.

A circuit is an arrangement of components or 'circuit elements'.

These elements might be arranged in a circle or even several joining circles or they might not.

Either way current might or might not flow, depending upon the nature of both the elements and the arrangement.

Oct 23rd 2017, 07:24 AM   #6
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 Originally Posted by avito009 So can a live wire, a person and the floor constitute a circuit?
Yes

 Originally Posted by avito009 Also tell me what is a circuit. I think a circuit is where there is a circular flow of electricity. But in the above case if it has to be a circuit the current flowing through a persons body and to the floor should return to the live wire. But i don't think that happens so how can this be a circuit?
It really is a circuit. The current flows through the matter in which the person is standing on, in this case a floor. If he was standing on a floor which consisted of a material made of an electric insulator then he wouldn't get shocked.

In electronics, a circuit is a path between two or more points along which an electrical current can be carried.

 Oct 23rd 2017, 11:23 AM #7 Senior Member     Join Date: Jun 2016 Location: England Posts: 366 The "normal" way to think of electrical flow is as a circuit of the battery, bulb and switch type. And electricity only flows if the circuit is complete. However, consider lightning. Where is the circuit here? Basically for an electrical flow, you need a region with a surfeit of electrons (an electron source), and a region with significantly fewer electrons where the surfeit can flow to (an electron sink). The battery provides this at its two terminals for the circuit, but the clouds and the ground provide the source and sink for lightning. In your original post you specified an alternating current. This means that the live wire is alternating between being an electron source and an electron sink. If the ground is suitably conductive, it can act as an electron "reservoir", so the live wire "sucks" electrons out of the ground, then "squirts" them back again. If you are in the middle, you can get a shock even though no (obvious) circuit has been made. studiot likes this. __________________ ~\o/~ Last edited by Woody; Oct 23rd 2017 at 11:26 AM.

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