Name: voltage balance in closed circuit loops
Uploaded: 2024-04-11T12:48:28.000Z
Duration: 1 min 4 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS+Phy.P4

HS+Phy.P4U1.8

Kirchhoff's Voltage Law

キルヒホッフの電圧法則(KVL)は、エネルギー保存の原理に基づいています。
これは、回路内の閉パスまたはループの周りのすべての電圧の代数的合計がゼロであることを示しています。
回路の周りのループの方向は、時計回りまたは反時計回りで、どこからでも開始できます。
ループ方向を選択すると、正の電圧には最初に負の端子が、負の電圧には正の端子が最初に接続されます。
各ループにKVLを適用し、項を並べ替えると、電圧降下の合計が供給された電圧の合計に等しいことを示す代替形式が得られます。
たとえば、直列に接続された 3 つの LED ライトがつながれているクリスマス ツリー ライトについて考えてみます。
各ライトが点灯するために3ボルトが必要な場合、バッテリーがこれらのライトに電力を供給するために必要な電圧は、KVLを印加することによって決定されます。
バッテリー電圧は、3つのライト間の電圧降下の合計に等しくなります。

キルヒホッフの電圧の法則

キルヒホッフの電圧法則 (KVL) は、物理学者グスタフ ロバート キルヒホッフによって導入された電気工学のもう 1 つの基本原則です。この法則は、エネルギーは生成も破壊もできず、ある形式から別の形式に移動または変換されるだけであるというエネルギー保存の原則に根ざしています。

KVL は、回路内の閉パスまたはループの周囲のすべての電圧の代数的合計がゼロであると述べています。これは、ループ内で供給される合計電圧が、そのループ内のコンポーネント間の合計電圧降下に等しいことを意味します。

回路の周囲のループの方向は時計回りまたは反時計回りで、どの点からでも開始できます。ループ方向が選択されると、負の端子が最初に現れる電圧が正の電圧となり、正端子が最初に現れる電圧が負の電圧になります。

KVL を時計回りに適用し、項を並べ替えると、別の法則が得られます。つまり、ループ内のコンポーネント間の電圧降下の合計が、供給される電圧の合計に等しくなります。

たとえば、直列に接続された 3 つの LED ライトが一緒につながれた家庭用照明システムを考えてみましょう。各ライトを点灯するには 3 ボルトが必要です。 KVL を適用することで、これらのライトに電力を供給するためにバッテリーに必要な電圧を決定できます。バッテリー電圧は 3 つのライトの電圧降下の合計、9 ボルトに等しくなります。

ただし、KVL が成り立つためには、重要な条件が満たされる必要があります。つまり、回路には 2 つの異なる電圧が等しくない限り、それらの電圧を並列に含めることはできません。これは、並列接続ではすべてのコンポーネントに同じ電圧がかかるため、不一致があるとエネルギー保存の法則に違反することになります。

キルヒホッフの電圧法則(KVL)は、エネルギー保存の原理に基づいています。
それは、閉じた...

Education

JoVE Core

Electrical Engineering

電気工学

Unit 1

ユニット1

Basics of Electric Circuits

電気回路の基礎

KEY TERMS AND CONCEPTS

主要用語および概念

voltage balance in closed circuit loops

Kirchhoff's Voltage Law explains how voltage is balanced in a closed circuit loop. It is a basic rule in electrical engineering and comes from the idea of energy conservation. Energy can change form, but it cannot be created or destroyed.

KVL states that the algebraic sum of all voltages around a closed path, or loop, is zero. In other words, the total voltage supplied in a loop equals the total voltage drop across the components in that loop. A loop can be traced clockwise or anticlockwise, and it can begin at any point.

The direction of the loop matters when you assign signs to voltages. If you meet the negative terminal first, the voltage is positive. If you meet the positive terminal first, the voltage is negative. When KVL is written in the clockwise direction and the terms are rearranged, the law can also be stated as the sum of voltage drops in a loop equals the sum of supplied voltages.

A simple household lighting example shows how KVL works. Three LED lights connected in series, with each light needing three volts, require a nine-volt battery to power them. The battery voltage matches the sum of the voltage drops across the three lights.

KVL also depends on an important circuit condition. A circuit cannot contain two different voltages in parallel unless those voltages are equal. In parallel connections, the same voltage appears across each component. If the voltages were different, the circuit would break the rule of energy conservation.

Voltage Balance in Closed Circuit Loops

charge and current

Electric Charge in Circuits

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voltage

Voltage in Electric Circuits

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power and energy

Circuit Power, Absorption, and Supply

Circuit power, absorption, and supply explain how much energy an element uses or delivers in an electric circuit. These ideas matter in electrical engineering because power and energy calculations help describe circuit behavior. A 100-watt light bulb, for example, emits more light than a 60-watt bulb, so wattage is a useful measure in real devices. Power is the time rate of expending or absorbing energy. It is measured in watts, written as W. The relation between power and energy uses the...

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Circuit Elements: Passive, Active, and Linear

Circuit elements are the building blocks of an electric circuit. An electric circuit is the connection of these elements. In this context, circuit elements are often grouped by how they behave and whether they supply energy. One major group is passive elements. These elements do not generate energy. Common passive elements include resistors, capacitors, and inductors. The other group is active elements, which can generate energy. Generators, batteries, and operational amplifiers are typical...

circuit terminology

Circuit Parts: Branches, Nodes, and Loops

Circuit parts like branches, nodes, loops, and meshes help describe how electrical networks work. An electrical network is a system of connected elements, such as resistors, capacitors, inductors, and voltage or current sources. Unlike a circuit, a network does not have to form a closed path. A circuit is also made of connected electrical elements, but it must include one or more closed paths. These loops let current flow continuously, which is what makes the circuit operate. Because of this,...

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Circuit Source Symbols and Controls

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ohm's law

Resistance and Conductance in Circuits

Resistance and conductance help explain how electric current moves through a circuit. Resistors are basic circuit parts made from metallic alloys or carbon compounds. They are used to model how a material resists current and to control and regulate electrical power in a circuit. Ohm's law describes the link between voltage and current across a resistor. The voltage across a resistor is directly proportional to the current through it. The constant that sets this relationship is resistance.

kirchhoff's current law

Kirchhoff's Current Law at Circuit Nodes

Kirchhoff's Current Law explains how current behaves at a circuit node. A node is the point where two or more circuit elements meet. The law says the current entering a node equals the current leaving it. That balance follows the rule of charge conservation, which means electric charge is not lost at the junction. When applying KCL, currents entering the node are treated as positive and currents leaving the node are treated as negative. The currents can be added algebraically at the node, and...

kirchhoff's voltage law

Kirchhoff's Voltage Law explains how voltage is balanced in a closed circuit loop. It is a basic rule in electrical engineering and comes from the idea of energy conservation. Energy can change form, but it cannot be created or destroyed. KVL states that the algebraic sum of all voltages around a closed path, or loop, is zero. In other words, the total voltage supplied in a loop equals the total voltage drop across the components in that loop. A loop can be traced clockwise or anticlockwise,...

voltage dividers

Series Resistors and Voltage Split

Series resistors split voltage across a circuit. In a series setup, resistors are linked one after another. The same current flows through each resistor in the chain. To analyze this behavior, Ohm's law is used to relate voltage, current, and resistance. Kirchhoff's voltage law says the voltages around a series loop add up to the source voltage. That means the current in the circuit equals the source voltage divided by the total resistance in series. The current value can then be used in Ohm's...

current dividers

Parallel Resistors and Current Division

Parallel resistors share the same two nodes, so each resistor has the same voltage across it. In this circuit setup, Kirchhoff's current law applies. The source current equals the sum of the currents through each branch. Ohm's law helps find the branch currents from the source voltage and the resistor values. The source current is equal to the source voltage times the sum of the reciprocals of the resistances. This makes it easier to calculate how current divides in the circuit. The current...

equivalent resistance

Delta-Wye Network Conversion

Delta-wye network conversion helps analyze resistor circuits that are not arranged in simple series or parallel paths. These three-terminal equivalent networks use the wye (Y), also called tee (T), and the delta (Δ), also called pi (π), as practical circuit models. These networks are useful in many circuit settings. They appear in three-phase electrical systems, electrical filters, and matching networks. They can also be used on their own or combined with more complex circuits. A delta...

design example: resistive touchscreen

Resistive Touchscreen Voltage Mapping

A resistive touchscreen uses voltage mapping to locate a finger touch on a mobile device. It is built from two metallic layers. The top layer is flexible, and the bottom layer is rigid. A narrow gap separates them, and the high resistance between the layers is an important part of the design. When a user touches the screen, the two layers meet at one point. That contact point is called the touchpoint. The touch lowers the resistance between the layers at that spot and changes the electrical...

key terms and concepts

Learn how Kirchhoff's Voltage Law balances voltage in a closed loop, how to assign signs, and why a series LED example needs a 9-volt battery.

Voltage Balance in Closed Circuit Loops | JoVE K12

JoVE Core 電気工学 は、電気回路の基本概念と回路解析テクニックを網羅したアニメーションビデオシリーズです。オペアンプと回路変換および 1 次・ 2 次回路の概念を網羅しています。実験を撮影した実写動画では、設計例や現代社会での応用が含まれており、複雑な概念も分かりやすく学習いただけます。

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Voltage Balance in Closed Circuit Loops

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