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- DictionaryCur·rent/ˈkərənt/
adjective
- 1. belonging to the present time; happening or being used or done now: "keep abreast of current events"
noun
- 1. a body of water or air moving in a definite direction, especially through a surrounding body of water or air in which there is less movement: "ocean currents"
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Electric Current is the rate of flow of electrons in a conductor. The SI Unit of electric current is the Ampere. Electrons are minute particles that exist within the molecular structure of a substance. Sometimes, these electrons are tightly held, and other times they are loosely held.
- 5 min
Sep 12, 2022 · The average electrical current I is the rate at which charge flows, Iave = ΔQ Δt, (9.2.1) where ΔQ is the amount of net charge passing through a given cross-sectional area in time Δt (Figure 9.2.1 ). The SI unit for current is the ampere (A), named for the French physicist André-Marie Ampère (1775–1836).
- Overview
- Charge
- Conductors and insulators
- Current
- Voltage
- Voltage resembles gravity
- Power
- Summary
Build an intuitive understanding of current and voltage, and power. Written by Willy McAllister.
Voltage and current are the cornerstone concepts in electricity. We will create our first mental models for these basic electrical quantities. We will also talk about power, which is what happens when voltage and current act together.
Charge
The concept of electricity arises from an observation of nature. We observe a force between objects, that, like gravity, acts at a distance. The source of this force has been given the name charge. A very noticeable thing about electric force is that it is large, far greater than the force of gravity. Unlike gravity, however, there are two types of electric charge. Opposite types of charge attract, and like types of charge repel. Gravity has only one type: it only attracts, never repels.
Conductors and insulators
Conductors are made of atoms whose outer, or valence, electrons have relatively weak bonds to their nuclei, as shown in this fanciful image of a copper atom. When a bunch of metal atoms are together, they gladly share their outer electrons with each other, creating a "swarm" of electrons not associated with a particular nucleus. A very small electric force can make the electron swarm move. Copper, gold, silver, and aluminum are good conductors. So is saltwater.
The concept of electricity arises from an observation of nature. We observe a force between objects, that, like gravity, acts at a distance. The source of this force has been given the name charge. A very noticeable thing about electric force is that it is large, far greater than the force of gravity. Unlike gravity, however, there are two types of...
Conductors are made of atoms whose outer, or valence, electrons have relatively weak bonds to their nuclei, as shown in this fanciful image of a copper atom. When a bunch of metal atoms are together, they gladly share their outer electrons with each other, creating a "swarm" of electrons not associated with a particular nucleus. A very small electric force can make the electron swarm move. Copper, gold, silver, and aluminum are good conductors. So is saltwater.
There are also poor conductors. Tungsten—a metal used for light bulb filaments—and carbon—in diamond form—are relatively poor conductors because their electrons are less prone to move.
Insulators are materials whose outer electrons are tightly bound to their nuclei. Modest electric forces are not able to pull these electrons free. When an electric force is applied, the electron clouds around the atom stretch and deform in response to the force, but the electrons do not depart. Glass, plastic, stone, and air are insulators. Even for insulators, though, electric force can always be turned up high enough to rip electrons away—this is called breakdown. That's what is happening to air molecules when you see a spark.
Semiconductor materials fall between insulators and conductors. They usually act like insulators, but we can make them act like conductors under certain circumstances. The most well-known semiconductor material is Silicon (atomic number 14 ). Our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones. The atomic-level details of how semiconductor devices work are governed by the theories of quantum mechanics.
Current is the flow of charge.
Charge flows in a current.
[Why did you say that twice?]
Current is reported as the number of charges per unit time passing through a boundary. Visualize placing a boundary all the way through a wire. Station yourself near the boundary and count the number of charges passing by. Report how much charge passed through the boundary in one second. We assign a positive sign to current corresponding to the direction a positive charge would be moving.
Since current is the amount of charge passing through a boundary in a fixed amount of time, it can be expressed mathematically using the following equation:
i=dqdt
To get our initial toehold on the concept of voltage, let's look at an analogy:
For a mass m , a change of height h corresponds to a change in potential energy, ΔU=mgΔh .
For a charged particle q , a voltage V corresponds to a change in potential energy, ΔU=qV .
Voltage in an electric circuit is analogous to the product of g⋅Δh . Where g is the acceleration due to gravity and Δh is the change of height.
A ball at the top of the hill rolls down. When it is halfway down, it has given up half of its potential energy.
An electron at the top of a voltage "hill" travels "downhill" through wires and elements of a circuit. It gives up its potential energy, doing work along the way. When the electron is halfway down the hill, it has given up, or "dropped", half of its potential energy.
For both the ball and the electron, the trip down the hill happens spontaneously. The ball and electron move towards a lower energy state all by themselves. On the trip down, there can be things in the way of the ball, like trees or bears to bounce off. For electrons, we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way.
Power is defined as the rate energy (U ) is transformed or transferred over time. We measure power in units of joules/second, also known as watts.
(1watt=1joule/second )
power=dUdt
An electric circuit is capable of transferring power. Current is the rate of flow of charge, and voltage measures the energy transferred per unit of charge. We can insert these definitions into the equation for power:
power=dUdt=dUdq⋅dqdt=vi
Electrical power is the product of voltage times current. in units of watts.
These mental models for current and voltage will get us started on all sorts of interesting electric circuits.
If you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage.
Apr 14, 2024 · Current, in the realm of electrical circuits, refers to the flow of electric charge through a conductor. It is the rate at which electrons move along a closed path, commonly a wire or circuitry. Measured in amperes (A), current is a fundamental concept in understanding the dynamic behavior of electricity.
noun. uk / ˈkʌr ə nt / us. current noun (AIR/WATER) the natural flow of air or water in one direction: a current of air. dangerous / strong currents. current noun (ELECTRICITY) the flow of electricity through a wire: an electrical current. (Definition of current from the Cambridge Learner's Dictionary © Cambridge University Press)
Feb 20, 2022 · We can use the definition of current in the equation \(I = \Delta Q / \Delta t\) to find the current in part (a), since charge and time are given. In part (b), we rearrange the definition of current and use the given values of charge and current to find the time required.
Current definition: passing in time; belonging to the time actually passing. See examples of CURRENT used in a sentence.
