Name: electrical current and electron drift
Uploaded: 2023-04-30T12:38:36.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability- Forces and Interactions

PS.PSc.6.2

Drift Velocity

導体内の自由電子はランダムな経路を移動し、他の電子や粒子と衝突します。
電場では、ランダムに動いた電子は、印加された電場とは反対の方向に徐々に漂流します。
したがって、電界による材料内の自由荷電粒子の平均速度は、ドリフト速度として知られています。これは、荷電粒子の濃度、各粒子の電荷の大きさ、および導体の断面積の積に対する導体内の電流の比率です。ドリフト速度のSI単位はメートル/秒です。
直径1mmの銅線を考えてみましょう。10 Aの電流がワイヤを通過するときのワイヤ内の電子の平均ドリフト速度はどれくらいですか?
まず、銅線内の自由電子の密度を計算します。銅中の自由電子の数は、立方メートルあたりの銅原子の数に等しくなります。次に、ワイヤの断面積を計算します。
項を並べ替えて置き換えることにより、ドリフト速度を決定できます。負の符号は、電荷が従来の電流とは反対方向に移動することを示します。

<ol>
	<li>OpenStaxです。(2019). 大学物理学 Vol.2.[Web版]、95-96ページ。<a href="https://openstax.org/books/university-physics-volume-2/pages/9-1-electrical-current" から取得>https://openstax.org/books/university-physics-volume-2/pages/9-1-electrical-current</a></li>
</ol>

ドリフト速度

電気信号の高速さは、電荷間の力が離れた場所で急速に作用するという事実から生じます。 したがって、自由電荷がワイヤに押し込まれると、入ってくる電荷は、同様の電荷間の反発力によって他の電荷を前方に押し出します。 これらの移動料金は、料金をさらに下流に移動させます。 系内の電荷密度は簡単には増加できないため、信号は急速に伝達されます。 結果として生じる電気衝撃波は、ほぼ光の速度で系内を移動します。 正確に言うと、この高速で移動する信号、または衝撃波は、電場の中で急速に伝播する変化です。 優れた車掌は無料の料金が多数あります。 金属では、自由電荷は自由電子です。 個々の電子が原子または他の電子と衝突するまでに移動できる距離は非常に短いです。 したがって、電子の経路は、ガス中の原子の動きのように、ほぼランダムに見えます。 しかし、導体には電場があり、電子は反対方向（マイナスに帯電しているため、電場とは反対）にドリフトします。 自由電荷の平均速度はドリフト速度として知られ、メートル/秒で表されます。 フリーチャージが非常に多いため、ドリフト速度は 10−4 m/s 程度と非常に小さくなります。 自由電子の衝突により、エネルギーが導体の原子に伝達されます。 電場は電子を遠くまで移動させる働きをしますが、その働きによって電子の運動エネルギーは増加しません。

移動する粒子の電荷は、マテリアルの種類に応じて正または負になります。 金属では、移動電荷は負 (電子) ですが、イオン化ガス (プラズマ) では、移動電荷には電子と正に帯電したイオンの両方が含まれる場合があります。 シリコンのような半導体の場合、伝導の一部は電子と正孔によって行われます。 正孔は、失われた電子の空孔サイトであり、正電荷のように機能します。 従来の電流は、導体内の自由電荷が正、負、またはその両方であるかどうかに関係なく、正電荷の流れとして扱われます。 一方、金属導体では、移動する電荷は電子ですが、電流は依然として正電荷の方向を向いて流れます。

電気信号の高速性は、電荷間の力が距離で急速に作用するという事実に起因します。したがって、無料充電が強制されると...

Education

JoVE Core

Physics

物理学

Unit 1

ユニット1

Current and Resistance

電流と抵抗

KEY TERMS AND CONCEPTS

主要用語と概念

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 shock wave. In a good conductor, there are many free charges available to carry that change along.

In metals, the free charges are free electrons. Each electron moves only a short distance before colliding with atoms or other electrons, so its path looks almost random. An electric field in the conductor gives the electrons a net drift in the direction opposite the field, because electrons are negatively charged.

The average speed of these free charges is called drift velocity. It is measured in meters per second and is very small, often around 10^-4 m/s, because so many free charges are present. Collisions transfer energy to the atoms of the conductor. The electric field does work on the electrons, but that work does not increase their kinetic energy.

The moving charges can be different in different materials. In metals, the charges are electrons. In an ionized gas, or plasma, the moving charges can include both electrons and positively charged ions. In a semiconductor such as silicon, conduction happens partly through electrons and holes, which are empty sites where electrons are missing and that act like positive charges.

Conventional current is treated as the flow of positive charge. This rule is used even when the real moving charges are negative, positive, or both. So in a metallic conductor, electrons move one way, but the current is still drawn in the direction that positive charges would move.

Electrical Current and Electron Drift

electrical current

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...

drift velocity

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 travels through conductors, why electron drift is slow, and how metals, plasma, and semiconductors carry charge.

Electrical Current and Electron Drift | JoVE K12

physics

JoVE Core 物理学は、運動学、力学、流体力学、静力学、波動、音響などの基礎的な物理学の理論と応用を、簡潔でわかりやすいアニメーション ビデオで紹介します。さらに、科学者の実際のビデオでは、世界中の今日の研究所で行われている古典的および独自の研究実験における関連概念の適用を示しています。

PS.PSc.6.3

PS.Phy.4.3

Tennessee Academic Standards

High School

Energy

PHYS.PS3.11

Virginia  Standards of Learning

HIgh School

PS.9

PS.9.b

PS.9.c

PH.8

PH.8.b

Alabama Course of Study Science

waves-and-their-applications-in-technologies-for-information-transfer

Waves and Their Applications in Technologies for Information Transfer

9-12.PS.2.3.c

9-12.PS.2.3.d

9-12.P.2.6.b

9-12.P.2.6.d

Florida Department of Education

SC.912.P.10

SC.912.P.10.15

Texas Essential Knowledge and Skills

PHYS.6

PHYS.6.D

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Energy

HS-PS3-6.

Position and Displacement

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Average Velocity

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Instantaneous Velocity - I

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Instantaneous Velocity - II

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Position and Displacement Vectors

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average-and-instantaneous-velocity-vectors

Average and Instantaneous Velocity Vectors

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Acceleration Vectors

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PS.PSc.4.1

Electrical Current

Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...

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Current Density

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Resistivity

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Resistance

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Ohm's Law

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Non-ohmic Devices

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Construct an explanation to compare simple series and parallel circuits in terms of Ohm's Law.

Continuity Equation

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Boundary Conditions for Current Density

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Electrical Conductivity

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Theory of Metallic Conduction

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Obtain, evaluate, and communicate information to explain how current is affected by changes in composition, length, temperature, and diameter of wire.

Magnetism

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Magnetic Fields

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Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the ...

Magnetic Flux

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motion-of-a-charged-particle-in-a-magnetic-field

Motion Of A Charged Particle In A Magnetic Field

A charged particle experiences a force when moving through a magnetic field. Consider the field to be uniform and the charged particle to move ...

Magnetic Force

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magnetic-force-on-a-current-carrying-conductor

Magnetic Force On A Current-Carrying Conductor

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magnetic-force-on-current-carrying-wires-example

Magnetic Force On Current-Carrying Wires: Example

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force-on-a-current-loop-in-a-magnetic-field

Force On A Current Loop In A Magnetic Field

Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical ...

torque-on-a-current-loop-in-a-magnetic-field

Torque On A Current Loop In A Magnetic Field

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The Hall Effect

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Magnetic Field due to Moving Charges

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Consider a point charge moving with a ...

Biot-Savart Law

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Biot-Savart Law: Problem-Solving

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Magnetic Field Due to Two Straight Wires

Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the ...

magnetic-force-between-two-parallel-currents

Magnetic Force Between Two Parallel Currents

Two long, straight, and parallel current-carrying conductors exert a force of equal magnitude on one another. The direction of the force depends on the ...

Magnetic Field Of A Current Loop

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Divergence and Curl of Magnetic Field

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To evaluate the divergence of the ...

Ampere's Law

A fundamental property of a static magnetic field is that it is not conservative, unlike an electrostatic field. Instead, there is a relationship between ...

Ampere's Law: Problem-Solving

Ampere&#x27;s law states that for any closed looped path, the line integral of the magnetic field along the path equals the vacuum permeability times the ...

Solenoids

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field for a solenoid is the ...

Magnetic Field of a Solenoid

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field due to a solenoid is ...

Toroids

A toroid is a closely wound donut-shaped coil constructed using a single&#xA0; conducting wire. In general, it is assumed that a toriod consists of ...

Use models to explain magnetism in terms of domains, interactions of poles, and magnetic fields.

PS.PSc.6.4

Analyze motion in terms of speed, velocity, acceleration, and momentum.

Electrical Current and Electron Drift

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