Name: current flow in simple circuits
Uploaded: 2023-04-30T12:38:29.000Z
Duration: 1 min 10 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

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Motion and Stability- Forces and Interactions

PS.PSc.6.2

Electrical Current

La velocità con cui scorre la carica è la corrente elettrica. L'unità SI per la corrente elettrica è l'ampere, che è definito come un coulomb di carica che passa attraverso un'area al secondo.
Prendi in considerazione una torcia con un interruttore, una lampadina, una batteria e dei cavi. L'interruttore controlla il circuito, mentre il filo fornisce un percorso di corrente tra i componenti.
Le rappresentazioni schematiche dei circuiti utilizzano simboli standardizzati e linee continue per rappresentare i singoli componenti del circuito e i fili di collegamento.
Il blub è rappresentato come un cerchio con un anello all'interno, che indica il filamento. L'interruttore è rappresentato come due punti con una barra conduttiva e la batteria come una serie di linee lunghe e corte.
Quando l'interruttore è chiuso, la torcia si accende poiché esiste un percorso completo per il flusso di carica dal terminale positivo a quello negativo della batteria.
La direzione della corrente convenzionale è sempre dal terminale positivo a quello negativo, mentre il flusso di elettroni va dal terminale negativo a quello positivo poiché gli elettroni sono caricati negativamente.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 2. [Versione web], pag 94 - 95. Estratto da <a href="https://openstax.org/books/university-physics-volume-2/pages/9-1-electrical-current">https://openstax.org/books/university-physics-volume-2/pages/9-1-electrical-current</a></li>
</ol>

la corrente elettrica

La corrente elettrica è definita come il tasso con cui fluisce la carica. Quando è presente una grande corrente, come quella utilizzata per far funzionare un frigorifero, una grande quantità di carica si sposta attraverso il filo in poco tempo. Se la corrente è piccola, come quella utilizzata per far funzionare una calcolatrice portatile, una piccola quantità di carica si muove attraverso il circuito per un lungo periodo di tempo. L'unità SI per la corrente è l'ampere (A), denominata in onore del fisico francese André-Marie Ampère (1775-1836). Un ampere è il flusso di un coulomb di carica attraverso un'area in un secondo. Una corrente di un ampere deriverebbe dal flusso di 6,25 × 1018 elettroni attraverso l'area ogni secondo. La maggior parte degli elettrodomestici è classificata in ampere (o ampere) necessari per un corretto funzionamento, così come gli interruttori automatici e i fusibili.

Considera un circuito semplice di una batteria per auto, un interruttore, una lampada per il faro e fili che forniscono un percorso per la corrente tra i componenti. Affinché la lampada si accenda, deve esserci un percorso completo per il flusso di corrente. L'interruttore è lì per controllare il circuito. Uno schema è una rappresentazione grafica di un circuito ed è molto utile per visualizzare le principali caratteristiche di un circuito. Gli schemi utilizzano simboli standardizzati per rappresentare i componenti in un circuito e linee continue per rappresentare i fili che collegano i componenti. La batteria è rappresentata come una serie di linee lunghe e corte, rappresentando la pila voltaica storica. La lampada è rappresentata come un cerchio con un anello all'interno, che rappresenta il filamento di una lampadina incandescente. L'interruttore è rappresentato come due punti con una barra conduttrice per collegare i due punti, e i fili che collegano i componenti sono rappresentati come linee continue.

Quando l'interruttore è chiuso, c'è un percorso completo per il flusso delle cariche, dal terminale positivo della batteria, attraverso l'interruttore, poi attraverso il faro e torna al terminale negativo della batteria. La direzione della corrente convenzionale è sempre rappresentata nella direzione in cui fluirebbe la carica positiva, dal terminale positivo al terminale negativo. Ad esempio, nei fili metallici, la corrente è trasportata dagli elettroni, cioè dalle cariche negative. Nelle soluzioni ioniche, come l'acqua salata, si muovono sia cariche positive che negative.

La corrente Elettrica

La corrente elettrica è definita come la velocità con cui scorre la carica. Quando è presente una grande corrente, come quella utilizzata per far funzionare un frigorifero, un grande ...

Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Current and Resistance

Corrente e Resistenza

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

current flow in simple circuits

Electrical current is the flow of charge in a circuit. A large current means a large amount of charge moves through a wire in a short time. A small current means only a small amount of charge moves through the circuit over a longer time. Examples include the current needed to run a refrigerator and the smaller current used by a handheld calculator.

The SI unit for current is the ampere, or amp. It is named for the French physicist André-Marie Ampère (1775–1836). One ampere means one coulomb of charge flows through an area in one second. A current of one amp would come from 6.25 × 10^18 electrons passing through that area each second. Most electrical appliances are rated in amperes, and fuses and circuit breakers are rated the same way for proper operation.

A simple circuit needs a complete path for current to flow. In a car battery circuit, the battery, switch, headlight lamp, and wires work together to make that path. The switch controls the circuit. When the switch is closed, charges can move from the positive terminal of the battery, through the switch, through the headlight, and back to the negative terminal.

Schematics help show this path with standard symbols. A battery is drawn as long and short lines, which represent the historic voltaic pile. A lamp is shown as a circle with a loop inside, and a switch is shown as two points with a conducting bar between them. The wires are shown as solid lines. Conventional current is drawn in the direction a positive charge would move, from positive to negative. In metal wires, electrons carry the current, so the moving charges are negative. In ionic solutions such as salt water, both positive and negative charges move.

Current Flow in Simple Circuits

electrical current

Electrical current is the flow of charge in a circuit. A large current means a large amount of charge moves through a wire in a short time. A small current means only a small amount of charge moves through the circuit over a longer time. Examples include the current needed to run a refrigerator and the smaller current used by a handheld calculator. The SI unit for current is the ampere, or amp. It is named for the French physicist André-Marie Ampère (1775–1836). One ampere means one coulomb of...

drift velocity

Electrical Current and Electron Drift

Electrical current in a conductor depends on moving charges and the tiny drift speed of those charges. When a free charge enters a wire, it pushes nearby charges ahead because like charges repel each other. That push spreads through the material very quickly, so the electrical signal moves through the system at nearly the speed of light. This fast signal is not the same as the slow motion of each charge. It is a rapidly spreading change in the electric field, often described as an electrical...

current density

Current Density in Wires and Solutions

Current density describes how much electric current passes through a given cross-sectional area. It helps show not just the size of the current, but also how it is distributed through a conductor. The current density can change from point to point because the local charge flow can vary. If the current flow is uniform, the amount of current is the same at every point along the conductor, even when the conductor’s area changes. Current density is measured in amperes per square meter. Its...

resistivity

Resistivity in Conductors and Insulators

Resistivity describes how much a material opposes electric current. When a voltage is applied to a conductor, an electric field forms. The charges in the conductor feel that force, and a current density develops. In some materials, including metals at a given temperature, the current density is approximately proportional to the electric field. In those cases, current density can be modeled with conductivity, written as sigma. Electrical conductivity is measured in (ohm·m)^−1. It tells how well...

resistance

Factors That Affect Electrical Resistance

Electrical resistance describes how much a conductor opposes the flow of current. It is represented by R. When current passes through a conductor, heat is also produced. Resistance is tied to the material’s resistivity, which is a property of the material used to make an electrical component. Resistance is different from resistivity. Resistivity belongs to the material itself, while resistance belongs to the finished component. To study this relationship, consider a wire with length L,...

ohm's law

Measuring Current, Voltage, and Resistance

Ohm's law describes the relationship between current, voltage, and resistance in many materials. In these cases, the current through a substance is directly proportional to the voltage applied to it. The idea was first shown experimentally by German physicist Georg Simon Ohm, who studied current in a metal wire. A material, component, or device that follows this pattern is called ohmic. An ohmic component has a current that increases in step with voltage. A material or component that does not...

non-ohmic devices

Diode Current and Reverse Bias

A diode is a nonohmic circuit element that makes current and voltage behave differently from Ohm’s law. In most substances, current is proportional to the voltage applied, but a diode does not show a linear current-voltage relationship. A diode is a semiconducting device with two terminals: an anode, which is the positive terminal, and a cathode, which is the negative terminal. It allows current to flow in only one direction. In a simple circuit with a battery, a diode, and a resistor, the...

electrical power

Power Limits in Electrical Circuits

Electrical power in a circuit depends on current and voltage. It is the product of these two values and is measured in watts, or joules per second. That relationship helps explain how much energy a circuit can deliver. A car’s auxiliary power outlet is one real-world example. Some outlets are rated at 20 amps and 12 volts, so they can deliver a maximum of 240 watts. That rating shows the upper limit of power the circuit can provide to devices such as a cell phone charger. Bulb wattage also...

electrical energy

Cutting Electric Bills with Efficient Lighting

Electrical energy is the energy transferred when electrons move from one point to another. The longer an appliance is used, the more electrical energy it consumes. If power stays constant, electrical energy equals the power used by the device times the time it runs. That is why longer use leads to a higher electric bill. Electric bills measure this energy in kilowatt-hours. One kilowatt-hour is equal to 3.6 × 10^6 joules. You can lower electrical energy use by cutting the time an appliance...

continuity equation

Charge Conservation and Current Flow

Charge conservation and current flow are linked through the continuity equation. The current density is the amount of current flowing per unit cross-sectional area. The current through a surface can be written as a surface integral of the current density. The conservation of charge says that the total current leaving a volume equals the rate at which charge inside that volume decreases. The total charge can be written using volume charge density, which is a space function. Because of this, the...

boundary conditions for current density

Current Density at Conductivity Boundaries

Current density at a boundary changes when two conducting materials have different electrical conductivities. The normal component of current density stays continuous across the interface. The tangential component, which runs along the surface, becomes discontinuous across the boundary. Consider two conducting media with conductivities σ1 and σ2 separated by an interface. At point P1 in medium 1, the steady current density makes an angle α1 with the normal. At point P2 in medium 2, the current...

electrical conductivity

Resistance and Ohm's Law in Conductors

Resistance and Ohm's law help explain how electric current moves through a conductor. In a perfect conductor, the electric field inside is zero because free electrons move to cancel it. Any extra charge then stays on the surface. In a practical conductor, an applied electric field can remain in place. That field drives electrons through the material and creates a current. The current density, which is current per unit area, is related to the electric field. More generally, it is related to the...

theory of metallic conduction

Electron Drift in Metallic Conduction

Electron drift in metallic conduction explains how free electrons move through a conductor. A classical model can describe this motion closely, even though quantum mechanics gives the best overall picture. This model is called the theory of metallic conduction. In this theory, Newton's second law is used to find the acceleration of an electron when an electric field is applied. The electron's velocity is then found from that acceleration. The electron travels through a crystal of positive ions...

key terms and concepts

Learn how electrical current flows in simple circuits, why amps matter, and how switches, batteries, and schematics show the path for charge.

Current Flow in Simple Circuits | JoVE K12

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Ohio’s Learning Standards and Model Curriculum

Energy And Waves

Electricity

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DC circuits

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Waves and Their Applications in Technologies for Information Transfer

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PS.PSc.6.4

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Current Flow in Simple Circuits

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