Name: current flow in simple circuits
Uploaded: 2023-04-30T12:38:29.000Z
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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

Electrical Current

معدل تدفق الشحنة هو التيار الكهربائي. وحدة النظام الدولي للوحدات للتيار الكهربائي هي الأمبير ، والذي يعرف بأنه كولوم واحد من الشحنة يمر عبر منطقة في الثانية.
ضع في اعتبارك مصباحا يدويا به مفتاح ومصباح وبطارية وأسلاك. يتحكم المفتاح في الدائرة ، بينما يوفر السلك مسارا حاليا بين المكونات.
تستخدم التمثيلات التخطيطية للدوائر رموزا قياسية وخطوطا صلبة لتمثيل مكونات الدائرة الفردية وأسلاك التوصيل.
يتم تمثيل blub على شكل دائرة بداخلها حلقة ، مما يشير إلى الفتيل. يتم تمثيل المفتاح كنقطتين مع شريط موصل والبطارية كسلسلة من الخطوط الطويلة والقصيرة.
عند إغلاق المفتاح ، يتم تشغيل المصباح اليدوي حيث يوجد مسار كامل لتدفق الشحن من الطرف الموجب إلى الطرف السالب للبطارية.
يكون اتجاه التيار التقليدي دائما من الطرف الموجب إلى الطرف السالب ، بينما يكون تدفق الإلكترون من الطرف السالب إلى الطرف الموجب حيث تكون الإلكترونات سالبة الشحنة.

<ol>
	<li>OpenStax. (2019). جامعة الفيزياء المجلد 2. [نسخة الويب] ، الصفحة 94 - 95. تم الاسترجاع من <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>

التيار الكهربائي

<div style="direction:rtl">يتم تعريف التيار الكهربائي على أنه المعدل الذي تتدفق به الشحنة. عندما يكون هناك تيار كبير، مثل ذلك المستخدم لتشغيل الثلاجة، فإن كمية كبيرة من الشحنة تتحرك عبر السلك خلال فترة زمنية قصيرة. إذا كان التيار صغيرًا، مثل ذلك المستخدم لتشغيل الآلة الحاسبة المحمولة، فإن كمية صغيرة من الشحنة تتحرك عبر الدائرة على مدى فترة طويلة من الزمن. وحدة قياس التيار في النظام الدولي للوحدات هي الأمبير (A)، والتي سميت على اسم الفيزيائي الفرنسي أندريه ماري أمبير (1775-1836). الأمبير هو تدفق كولوم واحد من الشحنة عبر منطقة ما في ثانية واحدة. سينتج تيار قدره أمبير واحد من 6.25 × 1018 يتدفق عبر المنطقة كل ثانية. يتم تصنيف معظم الأجهزة الكهربائية بالأمبيرات (أو الأمبيرات) اللازمة للتشغيل السليم، كما هو الحال مع الصمامات وقواطع الدائرة الكهربائية. فكر في دائرة بسيطة مكونة من بطارية سيارة، ومفتاح، ومصباح أمامي، وأسلاك توفر مسارًا للتيار بين المكونات. لكي يضيء المصباح، يجب أن يكون كاملاً مسار التدفق الحالي. المفتاح موجود للتحكم في الدائرة. التخطيطي هو تمثيل رسومي للدائرة وهو مفيد جدًا في تصور السمات الرئيسية للدائرة. تستخدم المخططات رموزًا موحدة لتمثيل المكونات في الدائرة وخطوطًا صلبة لتمثيل الأسلاك التي تربط المكونات. تظهر البطارية على شكل سلسلة من الخطوط الطويلة والقصيرة، تمثل الكومة الفولتية التاريخية. يظهر المصباح على شكل دائرة بداخلها حلقة، تمثل فتيل لمبة متوهجة. يظهر المفتاح على شكل نقطتين مع شريط توصيل لتوصيل النقطتين، وتظهر الأسلاك التي تربط المكونات على شكل خطوط متصلة. عند إغلاق المفتاح، يكون هناك مسار كامل لتدفق الشحنات، من الطرف الموجب للبطارية، عبر المفتاح، ثم عبر المصباح الأمامي والعودة إلى الطرف السالب للبطارية. يتم تمثيل اتجاه التيار الاصطلاحي دائمًا في الاتجاه الذي تتدفق فيه الشحنة الموجبة، من الطرف الموجب إلى الطرف السالب. على سبيل المثال، في الأسلاك المعدنية، يتم نقل التيار بواسطة الإلكترونات، أي الشحنات السالبة. وفي المحاليل الأيونية، مثل الماء المالح، تتحرك الشحنات الموجبة والسالبة.</div>

يعرف التيار الكهربائي بأنه معدل تدفق الشحنة. عندما يكون هناك تيار كبير ، مثل ذلك المستخدم لتشغيل الثلاجة ، فإن ...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

Current and Resistance

التيار والمقاومة

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

PS.PSc.6.3

PS.Phy.4.3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Energy And Waves

Electricity

Electricity And Magnetism

DC circuits

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

Arizona Science Standards

HS+Phy.P4

HS+Phy.P4U1.8

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

Next Generation Science Standards

Motion and Stability: Forces and Interactions

HS-PS2-5

Florida Department of Education

SC.912.P.10

SC.912.P.10.15

Texas Essential Knowledge and Skills

PHYS.6

PHYS.6.D

PHYS.6.E

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South Carolina College and Career Ready Science Standards

P-PS2-5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Energy

HS-PS3-6.

Georgia Standards of Excellence

SPS10.

Understanding Electrical Quantities

SP5.

Ohm’s Law

Position and Displacement

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Analyze and interpret data to explain the motion of an object moving with a constant velocity or that is accelerating.

PS.PSc.4.1

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 ...

Drift Velocity

The high speed of electrical signals results from the fact that the force between charges acts rapidly at a distance. Thus, when a free charge is forced ...

Current Density

The total amount of current flowing through one unit value of a cross-sectional area is referred to as current density. If the current flow is uniform, ...

Resistivity

When a voltage is applied to a conductor, an electrical field is generated, and charges in the conductor feel the force due to the electrical field. The ...

Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

Ohm's Law

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm&#8217;s law. The current that flows ...

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

The total amount of current flowing per unit cross-sectional area is called the current density. Hence, the current passing through a cross-sectional area ...

Boundary Conditions for Current Density

Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current ...

Electrical Conductivity

In perfect conductors, the electric field inside is always zero due to the abundance of free electrons, which nullify any field by flowing. As a result, ...

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

The magnetic flux measures the number of magnetic field lines passing through a given surface area. The SI unit for magnetic flux is the weber (Wb). ...

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

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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 ...

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Torque On A Current Loop In A Magnetic Field

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The Hall Effect

Edwin H. Hall, in the year 1879, devised an experiment that could be used to identify the polarity of the predominant charge carriers in a conducting ...

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a ...

Biot-Savart Law

The Biot-Savart law gives the magnitude and direction of the magnetic field produced by a current. This empirical law was named in honor of two ...

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.

Current Flow in Simple Circuits

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