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For charge to flow there must be an area of higher electrical potential energy, an area of lower electrical potential energy and a conduction path. So for a simple circuit of say a battery and a wire. If we connect the wire from the positive to the negative terminals of the battery, charge can then flow along the wire from the area of high potential to the area of low potential. Remember potential is relative not absolute. So potential is measured between two points. An analogy is water flowing down a hill. If we have a bucket of water half way up a hill it is at lower gravitational potential energy to all the points higher up the hill. It is at a higher gravitational potential to points lower down the hill. The potential difference is given by the height between your bucket and the other place on the hill. If we connect a hose to the bucket with the other end lower down the hill water will flow from the area of higher gravitational potential to the area of lower gravitational potential. The height difference between the two points is what is crucial and what will force the water down the hose. Not the height of either place say in reference to the ground. . http://www.furryelephant.com/content/electricity/complete-circuits/ . I am not sure what you mean when asking about standing on the ground barefoot. If you feel a current flowing then there must be a potential energy difference between your feet. This can certainly happen, and is an important thing to remember if say there is lightning about. If lightning hits the ground near you, where it strikes will most likely be at a greatly different potential to where you are. Current will flow through the ground according to that potential difference, and the resistance of the ground. V=IR So the current that flows is proportional to the potential difference V, and inversely proportional to the resistance R. The R of the earth is reasonably low, and the V near a lighting strike is likely to be large. So there will be a large potential difference from where the lightning struck to some point a long way away. For every point in between there will also be a potential difference, generally getting smaller the closer the two points are together. So if the potential difference between the point of the strike, which we will call 0m, and a point 1000m away was say 100 000V (just a made up number), the the potential difference between 0m and 500m might be 70 000v (again, just a made up number but the drop off is unlikely to be linear). Now at all points in between there will also be a potential difference. So the point 100m away and the point 101m away will have a potential difference between them and current will be flowing. If you have one foot at 100m and the other at 101m then your feet will be at different potentials and a current may flow from one foot through your body to the other foot. For this reason it is recommended if caught in a lightning storm to crouch low with your feet close together. This minimises the likelihood of lighting striking you, and if lightning strikes close by minimises the potential difference that will be between your feet.

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