6/24/2023 0 Comments Define current voltage resistance![]() ![]() For example, the voltage of a battery, which is stable over a long period of time, will be symbolized with a capital letter “E,” while the voltage peak of a lightning strike at the very instant it hits a power line would most likely be symbolized with a lower-case letter “e” (or lower-case “v”) to designate that value as being at a single moment in time. The “I” is thought to have been meant to represent “Intensity” (of electron flow), and the other symbol for voltage, “E,” stands for “Electromotive force.” From what research I’ve been able to do, there seems to be some dispute over the meaning of “I.” The symbols “E” and “V” are interchangeable for the most part, although some texts reserve “E” to represent voltage across a source (such as a battery or generator) and “V” to represent voltage across anything else.Īll of these symbols are expressed using capital letters, except in cases where a quantity (especially voltage or current) is described in terms of a brief period of time (called an “instantaneous” value). The “R” for resistance and the “V” for voltage are both self-explanatory, whereas “I” for current seems a bit weird. ![]() The mathematical symbol for each quantity is meaningful as well. Ampere, the volt after the Italian Alessandro Volta, and the ohm after the German Georg Simon Ohm. And, yes, that strange-looking “horseshoe” symbol is the capital Greek letter Ω, just a character in a foreign alphabet (apologies to any Greek readers here).Įach unit of measurement is named after a famous experimenter in electricity: The amp after the Frenchman Andre M. The “unit abbreviation” for each quantity represents the alphabetical symbol used as a shorthand notation for its particular unit of measurement. Standardized letters like these are common in the disciplines of physics and engineering, and are internationally recognized. The “symbol” given for each quantity is the standard alphabetical letter used to represent that quantity in an algebraic equation. Here are the standard units of measurement for electrical current, voltage, and resistance: For mass, we might use the units of “kilogram” or “gram.” For temperature, we might use degrees Fahrenheit or degrees Celsius. To be able to make meaningful statements about these quantities in circuits, we need to be able to describe their quantities in the same way that we might quantify mass, temperature, volume, length, or any other kind of physical quantity. For this reason, the quantities of voltage and resistance are often stated as being “between” or “across” two points in a circuit. Just like voltage, resistance is a quantity relative between two points. The amount of current in a circuit depends on the amount of voltage available to motivate the electrons, and also the amount of resistance in the circuit to oppose electron flow. This opposition to motion is more properly called resistance. Without reference to two particular points, the term “voltage” has no meaning.įree electrons tend to move through conductors with some degree of friction, or opposition to motion. ![]() When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move electrons from one particular point in that circuit to another particular point. Voltage is a specific measure of potential energy that is always relative between two points. The force motivating electrons to “flow” in a circuit is called voltage. This continuous movement of free electrons through the conductors of a circuit is called a current, and it is often referred to in terms of “flow,” just like the flow of a liquid through a hollow pipe. ![]() \)Īn electric circuit is formed when a conductive path is created to allow free electrons to continuously move. ![]()
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