# Equipotential Lines...

by franz32
Tags: equipotential, lines
 P: 133 This is the same equipotential lines thread that you may have read in the Linear and Abstract Algebra. I have questions… 1. Why don't birds sitting on power cables atop transmission posts get electrocuted? Why do boys get electrocuted when the thread of the kite they are flying accidentally touches a power cable? 2. When you walk across a carpeted floor and then hold the door knob, you are more likely to get an electric shock. Why? Where does the current come from? 3. What do the lines of force surrounding a point charge represent? 4. How do I draw equipotential lines surrounding a point charge? 5. How do I draw the lines of force surrounding a point charge? 6. When you get caught at the middle of a thunder storm in an open field, you usually take refuge under a tree lying down. How should you lie down so you won't get a shock if ever the tree is hit? =)
 Emeritus Sci Advisor PF Gold P: 7,332 1. Birds do not get electrocuted because they are at the same potential as the line they are sitting on. There is no potential difference to create a current flow. 2. The kite string completes a circuit from the wire at an elevated electrical potential to ground. The person holding the string becomes part of the circuit. 3. The variation of the electric field strength? 4. In 2d, as circles, in 3d as spheres. 5. DO NOT lay under a tree during an electrical storm. If you are concerned about lighting lay flat on the ground WELL AWAY from any trees. If there is a tree near by, lay or stand, on a tangent to a circle concentric to the tree, do not lay on a radial line. Lighting strikes create a huge potential gradient in the ground surrounding the strike. If you are laying, or standing so all parts of your body are equidistant from the center of the strike (ie on an exponential line) you will be in less danger then if part of your body is closer to the strike.
P: 211
 Originally posted by Integral 5. DO NOT lay under a tree during an electrical storm. If you are concerned about lighting lay flat on the ground WELL AWAY from any trees. If there is a tree near by, lay or stand, on a tangent to a circle concentric to the tree, do not lay on a radial line. Lighting strikes create a huge potential gradient in the ground surrounding the strike. If you are laying, or standing so all parts of your body are equidistant from the center of the strike (ie on an exponential line) you will be in less danger then if part of your body is closer to the strike.
I think related to the potential gradient you mention, the advice I see most often is to *not* lie down but to squat as low as you can with only your feet touching the ground. That's hard for most americans.

 Emeritus Sci Advisor PF Gold P: 7,332 Equipotential Lines... Yes, you would be better off squatting. The maximum distance between you "points" of contact would determine the potential difference across your body. What ever the gradient in the ground is, the smaller distance you span the safer you are.
 P: 133 As to my "history", my 2nd year teacher told me that birds don't get electrocuted because their feet are somewhat insulated... I don't know if he's right.
Math
Emeritus