Name: measuring current, voltage, and resistance
Uploaded: 2023-04-30T12:39:07.000Z
Duration: 1 min 21 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

Ohm's Law

В 1827 году немецкий физик Георг Симон Ом экспериментально продемонстрировал закон Ома.
Закон Ома гласит, что ток, проходящий через материал, прямо пропорционален напряжению на устройстве при постоянных окружающих условиях.
Любой материал, который подчиняется закону Ома, известен как омический материал, в то время как если он не подчиняется закону Ома, он известен как неомический материал.
Рассмотрим еще одну экспериментальную установку, демонстрирующую закон Ома, состоящую из резистора, источника питания, переключателя, вольтметра и амперметра. Напряжение на резисторе измеряется с помощью вольтметра, а ток на линии с резистором измеряется с помощью амперметра.
Когда резистор подключен к источнику питания, ток протекает по часовой стрелке, а вольтметр и амперметр показывают положительные показания. И наоборот, при переключении выводов источника питания ток протекает против часовой стрелки, что приводит к отрицательным показаниям.
График, построенный между показаниями напряжения и тока, оказывается линейным. Наклон линии дает сопротивление, подтверждая, что резистор является омическим устройством.

<ol>
	<li>OpenStax. (2019). Университетская физика Том 2. [Веб-версия], стр. 396–398. Получено из <a href="https://openstax.org/books/university-physics-volume-2/pages/9-4-ohms-law">https://openstax.org/books/university-physics-volume-2/pages/9-4-ohms-law</a></li>
</ol>

Закон Ома

Многие материалы проявляют простую взаимосвязь между значениями тока, напряжения и сопротивления, известную как закон Ома. Ток, проходящий через большинство веществ, прямо пропорционален напряжению, поданному на них. Немецкий физик Георг Симон Ом (1787-1854) первым экспериментально доказал, что ток в металлической проволоке прямо пропорционален поданному напряжению. Любой материал, компонент или устройство, которое подчиняется закону Ома, где ток через устройство пропорционален поданному напряжению, известно как омический материал или омический компонент. Любой материал или компонент, не подчиняющийся закону Ома, известен как неомический материал или неомический компонент. В статье, опубликованной в 1827 году, Георг Ом описал эксперимент, в котором он измерял напряжение и ток через различные простые электрические цепи, содержащие различные длины провода. Эксперимент использовался для наблюдения тока через резистор, возникающего из-за приложенного напряжения.

Другой похожий эксперимент использовался для наблюдения тока через резистор, возникающего из-за приложенного напряжения. В этой простой схеме резистор подключён последовательно с батареей. Напряжение измеряется вольтметром, который помещается параллельно резистору. Ток измеряется амперметром и помещается последовательно с резистором. Были произведены несколько измерений тока для нескольких разных напряжений. Измеряли ток через резистор и напряжение на резисторе, построился график между напряжением и током, который показал примерно линейную зависимость. Угловой коэффициент прямой - это сопротивление или напряжение, делённое на ток. Результат стал известен как закон Ома.

Многие материалы демонстрируют простую зависимость между значениями тока, напряжения и сопротивления, известную как закон Ома. Течение, которое течет...

Education

JoVE Core

Physics

Физика

Unit 1

Раздел 1

Current and Resistance

Ток и сопротивление

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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 follow this pattern is called nonohmic.

Ohm's 1827 experiment measured voltage across and current through simple electrical circuits with different wire lengths. The setup used a resistor connected in series with a battery. A voltmeter measured voltage in parallel with the resistor, and an ammeter measured current in series with the resistor.

Several measurements were taken at different voltages. The current through the resistor and the voltage across it were then graphed. The result was an approximately linear relationship. The slope of that line represents resistance, which is voltage divided by current, and this result became known as Ohm's law.

Measuring Current, Voltage, and Resistance

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 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

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

See how Ohm measured current and voltage in a simple circuit, why some materials are ohmic, and how the graph slope reveals resistance.

Measuring Current, Voltage, and Resistance | JoVE K12

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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.Phy.4.3

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Ohio’s Learning Standards and Model Curriculum

Energy And Waves

Electricity

Electricity And Magnetism

DC circuits

Tennessee Academic Standards

High School

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PHYS.PS3.11

PHYS.PS3.12

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PH.8

PH.8.b

Arizona Science Standards

HS+Phy.P4

HS+Phy.P4U1.8

Alabama Course of Study Science

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Waves and Their Applications in Technologies for Information Transfer

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9-12.PS.2.3.d

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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.E

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New York State Science Learning Standards

HS. Energy

HS-PS3-6.

Georgia Standards of Excellence

SPS10.

Ohm’s Law

SP5.

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Non-ohmic Devices

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PS.PSc.6.4

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

Measuring Current, Voltage, and Resistance

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