Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light. Fluke virtual demos and product selectors.It pretty much does not matter how long the hose is. No matter how long the garden hose the water comes out the end at a high pressure (high voltage). It's similar to the difference between pouring water from a height (high voltage) onto the ground (low voltage) compared to flowing water constantly through a garden hose. What they actually do is continuously raise electrons to a high voltage and force them into the transmission lines, actively pushing the wires full of electrons. If that was the case then yes, the voltage would drop if you live farther away from the power station. They don't collect a big pile of electrons as the fixed charge and repel some free electrons into the transmission lines. ![]() However, power generated by the electric utility is not using this simple setup. The farther away the test charge gets the lower its potential and the lower its voltage. One charge is in a fixed location and a second test charge is moved toward and away from the other. The formal definition of voltage is based on two positive charges near each other. Nearby electrons are attracted and move toward the positive terminal. There is a different chemical reaction happening at the positive terminal that absorbs electrons, creating a deficit of electrons for a net positive charge in the region near that terminal. Electrons in the wire are repelled from this concentration and move away, towards the positive battery terminal. A chemical reaction near the negative terminal of a battery releases an excess number of electrons in the vicinity (in the attached wire). In a circuit, charges move because they are repelled from like charges and attracted to unlike charges. If I do the experiment with a charged balloon, I can use my hand to push the charged object towards another. In this general definition of of electric potential you can imagine any external force you want pushing the charge. (If it accelerates then all sorts of new physics starts to happen involving magnetism, which at the moment is way over our heads.) For now we make our charges sit still (static) or we move them super slow where they move but they don't accelerate, a condition called "pseudo-static". It is important not to push too long or too hard because we don't want the charged particle to accelerate. If you want to actually move a charge, you have to apply an ever-so-slightly greater force to the charge to get it to start moving. ![]() In almost all circuits, the second point is provided and this absolute idea isn't needed. It's the same voltage as usual, but with the assumption that the starting point is infinity away. A common choice that lots of engineers and scientists make is "A is infinity away from the charged object." When we make that choice, we say we are determining the absolute potential energy, or the absolute voltage. If I don't give it to you, you have to make one up. What if I told you where B was but did not mention A? I might say it this way: "What is the potential energy of a test charge when you place it at B"? Well, you need an A to answer that question. There are just a few oddball situations that give us some trouble. To use this equation you have to put in two locations, A and B. For example, you could be moving your test charge towards or away from some charged object. That equation tells you how electric potential energy changes when you move a test charge from point A to point B. ![]() Go back to the equation for Electric Potential Energy Difference (AB) in the middle of the section on Electric Potential Energy. Electric potential energy difference A B = ∫ r A r B − q E ⃗ ⋅ d r = q Q 4 π ϵ 0 ( 1 r B − 1 r A ) \displaystyle \text \right ) electric potential energy difference A B = ( 4 π ϵ 0 q Q r B 1 ) − ( 4 π ϵ 0 q Q r A 1 ) start text, e, l, e, c, t, r, i, c, space, p, o, t, e, n, t, i, a, l, space, e, n, e, r, g, y, space, d, i, f, f, e, r, e, n, c, e, end text, start subscript, A, B, end subscript, equals, left parenthesis, start fraction, q, Q, divided by, 4, pi, \epsilon, start subscript, 0, end subscript, end fraction, start fraction, 1, divided by, r, start subscript, B, end subscript, end fraction, right parenthesis, minus, left parenthesis, start fraction, q, Q, divided by, 4, pi, \epsilon, start subscript, 0, end subscript, end fraction, start fraction, 1, divided by, r, start subscript, A, end subscript, end fraction, right parenthesis
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