Name: cutting electric bills with efficient lighting
Uploaded: 2023-09-18T17:11:16.000Z
Duration: 1 min 10 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

HS-PS2-5

Electrical Energy

A energia elétrica pode ser definida como a energia causada pelo movimento dos elétrons de um ponto a outro.
A quantidade de energia elétrica pode ser determinada pela energia usada por um dispositivo durante um intervalo de tempo específico.
A unidade SI de energia elétrica é o joule, ou watt-segundo, enquanto a unidade comercial é o quilowatt-hora, também conhecido como unidade da Junta Comercial.
Considere uma lâmpada incandescente de 60 watts e uma lâmpada LED de 20 watts, cada uma produzindo uma quantidade equivalente de luz.
Determine a economia de custos na substituição da lâmpada incandescente pela lâmpada LED funcionando por 4 horas diárias durante 365 dias, assumindo que 12 centavos por quilowatt-hora é a tarifa média de energia cobrada pela empresa de energia.
Primeiro, determine individualmente a quantidade de energia elétrica consumida pela lâmpada incandescente e pela lâmpada LED.
Em segundo lugar, multiplique a energia consumida pela lâmpada individual pelo custo cobrado pela empresa de energia.
A lâmpada LED usa três vezes menos energia e economiza cerca de US$ 7,00 em comparação com a lâmpada incandescente.

<ol>
	<li>OpenStax. (2019). Física Universitária Vol. 2. [Versão Web], Pg 396 - 398. Obtido de <a href="https://openstax.org/books/university-physics-volume-2/pages/9-5-electrical-energy-and-power">https://openstax.org/books/university-physics-volume-2/pages/9-5-electrical-energy-and-power</a></li>
</ol>

energia elétrica

Usar aparelhos elétricos por um período mais longo consome mais energia elétrica e resulta em uma conta de luz mais alta. A energia produzida pela transferência de elétrons de um ponto para outro é conhecida como energia elétrica. Se a potência for entregue em uma taxa constante, a energia elétrica pode ser definida como o produto da potência utilizada pelo dispositivo por um período de tempo. A unidade de energia nas contas de luz é o quilowatt-hora, onde um quilowatt-hora é equivalente a 3,6 x 106 joules. A energia elétrica (E) utilizada pode ser reduzida tanto reduzindo o tempo de uso quanto reduzindo o consumo de energia desses aparelhos ou dispositivos. Isso não apenas reduz o custo, mas também resulta em um impacto reduzido no meio ambiente.

A iluminação consome cerca de 20% da energia utilizada em casas e aproximadamente 40% em edifícios comerciais. A eficiência da iluminação fluorescente é aproximadamente quatro vezes maior do que a da iluminação incandescente, tanto para tubos longos quanto para lâmpadas fluorescentes compactas. A transferência de calor dessas lâmpadas fluorescentes compactas (CFLs) é menor, e elas duram até 10 vezes mais do que as lâmpadas incandescentes. As modernas lâmpadas de diodo emissor de luz (LED) de luz branca, que consistem em um número de pequenas lâmpadas LED agrupadas, são ainda mais eficazes e duram cinco vezes mais do que as lâmpadas fluorescentes compactas.

A maneira mais simples de reduzir o consumo de energia em residências e edifícios comerciais é trocar as lâmpadas incandescentes por CFLs ou lâmpadas de LED. As lâmpadas CFL operam com um mecanismo muito diferente das luzes incandescentes, contendo vapor de argônio e mercúrio alojados em um tubo em forma de espiral. Elas utilizam um "balastro" que aumenta a tensão usada pela lâmpada CFL. O balastro produz uma corrente elétrica, que passa pela mistura de gases e excita as moléculas de gás. As moléculas de gás excitadas produzem luz ultravioleta (UV), que por sua vez estimula o revestimento fluorescente no interior do tubo. Esse revestimento fluoresce no espectro visível, emitindo luz visível. Embora essas lâmpadas contenham mercúrio, que é venenoso, o mercúrio nunca será liberado desde que a lâmpada não quebre. Mesmo se a lâmpada quebrar, o mercúrio tende a permanecer no revestimento fluorescente. E é uma quantidade muito pequena, de forma que o benefício de economizar energia pode superar a desvantagem de usar mercúrio.

Energia Elétrica

O uso de aparelhos elétricos por um longo período de tempo consome mais energia elétrica e resulta em uma conta de luz mais alta. A energia produzida pelo ...

Education

JoVE Core

Physics

Física

Unit 1

Unidade 1

Current and Resistance

Corrente e Resistência

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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 runs or by choosing a device that uses less power. Both changes can lower cost and reduce environmental impact.

Lighting is a major part of energy use. It accounts for about 20% of the energy used at home and close to 40% in commercial buildings. Fluorescent lighting is about four times more efficient than incandescent lighting. This applies to both long fluorescent tubes and compact fluorescent lights, or CFLs.

CFLs give off less heat and last up to 10 times longer than incandescent bulbs. Modern white light-emitting diode, or LED, lights are even more effective. They are made of many tiny LED bulbs grouped together, and they can last five times as long as CFL bulbs. The easiest way to reduce energy use in homes and commercial buildings is to switch from incandescent bulbs to CFL or LED bulbs.

CFL bulbs work very differently from incandescent lights. They contain argon and mercury vapor inside a spiral-shaped tube. A ballast raises the voltage used by the CFL and creates an electric current. That current excites the gas molecules, which produce ultraviolet light. The UV light then makes the fluorescent coating on the inside of the tube glow in visible light.

CFL bulbs do contain mercury, which is poisonous, but it is not released as long as the bulb stays intact. Even if the bulb breaks, the mercury usually remains in the fluorescent coating. The amount is very small, and the energy saved may outweigh the drawback of using mercury.

Cutting Electric Bills with Efficient Lighting

cutting-electric-bills-with-efficient-lighting

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

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

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 energy use affects electric bills and why CFL and LED bulbs can reduce power use, heat, and cost in homes and schools.

Cutting Electric Bills with Efficient Lighting | JoVE K12

physics

JoVE Core - Fisica apresenta a teoria e a aplicação de tópicos fundamentais da física, incluindo cinemática, dinâmica, mecânica dos fluidos, estática, ondas e acústica, com vídeos animados concisos e de fácil compreensão. Além disso, os vídeos de cientistas em ação demonstram a aplicação de conceitos relacionados em experimentos de pesquisa clássica e original realizados nos laboratórios de todo o mundo hoje em dia.

Florida Department of Education

SC.912.P.10

SC.912.P.10.15

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

P-PS2-5

Georgia Standards of Excellence

9-12

SPS7.

Types of Energy

Force

Forces affect every moment of our life. Our bodies are held to the Earth by force, and they are held together by the forces of charged particles. When we ...

Types of Forces

In most situations, forces can be grouped into two categories: contact forces and field forces.&#160; Contact forces occur as a result of direct physical ...

Internal and External Forces

Newton&#39;s first law states that a net external force causes a change in motion. External forces act on an object or system, originating outside of the ...

Newton's Second Law

Newton&#39;s second law is closely related to his first law of motion. It mathematically gives the cause-and-effect relationship between force and changes ...

Second Law: Motion under Same Force

Newton&#39;s laws can be applied to bodies at rest and bodies in motion. Newton&#39;s first law is applied to bodies in equilibrium, whereas the second ...

second-law-motion-under-same-acceleration

Second Law: Motion under Same Acceleration

Newton&#39;s second law of motion applies to bodies moving under the same acceleration. For example, when a baggage tractor pulls luggage carts, each cart ...

Force and Acceleration

Source: Nicholas Timmons,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of California, Irvine, ...

Newton's Laws of Motion

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment examines at various situations involving two interacting ...

Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object sliding down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]

HS-PS2-1

Inertial Frames of Reference

Newton&#8217;s first law is usually considered to be a statement about reference frames. It provides a method for identifying a special type of reference ...

Non-inertial Frames of Reference

A reference frame accelerating or decelerating relative to an inertial frame is a non-inertial frame. To help understand this, consider what taking off in ...

Linear Momentum

The term momentum is used in various ways in everyday language, most of which are consistent with the precise scientific definition. Generally, momentum ...

Force and Momentum

Force and momentum are intimately related. Force acting over time can change momentum, and Newton&#39;s second law of motion can be stated in its most ...

Impulse

According to Newton&#8217;s second law of motion, the rate of change of the momentum of an object is the net external force acting on it. The total change ...

Impulse-Momentum Theorem

The total change in the motion of an object is proportional to the total force vector acting on it and the time over which it acts. This product is called ...

Conservation of Momentum: Introduction

The total momentum of a system consisting of N interacting objects is constant in time or is conserved. A system must meet two requirements for its ...

Conservation of Momentum: Problem Solving

Solving problems using the conservation of momentum requires four basic steps:

	Identify a closed system, where the total mass is constant, and no net ...

Conservation of Momentum

Types Of Collisions - I

When two objects come in direct contact with each other, it is called a collision. During a collision, two or more objects exert forces on each other in a ...

Types of Collisions - II

When two or more objects collide with each other, they can stick together to form one single composite object (after collision). The total mass of the ...

Elastic Collisions: Introduction

An elastic collision is one that conserves both internal kinetic energy and momentum. Internal kinetic energy is the sum of the kinetic energies of the ...

Elastic Collisions: Case Study

Elastic collision of a system demands conservation of both momentum and kinetic energy. To solve problems involving one-dimensional elastic collisions ...

collisions-in-multiple-dimensions-introduction

Collisions in Multiple Dimensions: Introduction

It is far more common for collisions to occur in two dimensions; that is, the initial velocity vectors are neither parallel nor antiparallel to each ...

collisions-in-multiple-dimensions-problem-solving

Collisions in Multiple Dimensions: Problem Solving

In multiple dimensions, the conservation of momentum applies in each direction independently. Hence, to solve collisions in multiple dimensions, we should ...

Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system. [Clarification Statement: Emphasis is on the quantitative conservation of momentum in interactions and the qualitative meaning of this principle.] [Assessment Boundary: Assessment is limited to systems of two macroscopic bodies moving in one dimension.]

HS-PS2-2

Free-body Diagram

In mechanics, understanding the motion of objects is essential, and one tool that helps solve this problem is the free-body diagram. It is a simple but ...

Steps for Free-Body Diagram

When it comes to studying the behavior of objects in mechanics, one of the most important tools available is the free-body diagram. Consider a simple ...

Free-body Diagrams: Problem Solving

Free-body diagrams are essential tools for physicists and engineers studying the motion of objects. Free-body diagrams are graphical representations of ...

Design Consideration

While designing a structure, the considerations start with the ultimate strength of a material, which is determined through tests, measuring changes under ...

Apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision. [Clarification Statement: Examples of evaluation and refinement could include determining the success of the device at protecting an object from damage and modifying the design to improve it. Examples of a device could include a football helmet or a parachute.] [Assessment Boundary: Assessment is limited to qualitative evaluations and/or algebraic manipulations.]

HS-PS2-3

Gravitation

In the years before Newton, a general belief prevailed that different laws governed objects in the sky than objects on Earth. When Kepler wrote down the ...

/files/media/science-education/science-education-thumbs/14716.jpg

Newton's Law of Gravitation

Our everyday observation tells us that all objects close to the Earth naturally tend to fall to the ground. Early philosophers assumed that this downward ...

Newton's Law of Universal Gravitation

Source: Ketron Mitchell-Wynne, PhD,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of ...

Coulomb's Law

Experiments with electric charges have shown that if two objects each have an electric charge, they exert an electric force on each other. The magnitude ...

coulomb-s-law-and-the-principle-of-superposition

Coulomb's Law and The Principle of Superposition

Coulomb&#39;s Law describes the force experienced by two point charges under each other&#39;s presence. But what if there are more than two charges? For ...

comparison-between-electrical-and-gravitational-forces

Comparison Between Electrical And Gravitational Forces

There are four fundamental forces in nature: the gravitational force, the electromagnetic force, the strong nuclear force, and the weak nuclear force. To ...

Gravity between Spherical Bodies

Newton&#39;s law of gravitation describes the gravitational force between any two point masses. However, for extended spherical objects like the Earth, ...

the-principle-of-superposition-and-the-gravitational-field

The Principle of Superposition and the Gravitational Field

The principle of superposition applies to gravitational forces of objects that are sufficiently far apart. It states that the net gravitational force on a ...

/files/media/science-education/science-education-thumbs/14754.jpg

Electric Field

Consider two point charges, each exerting Coulomb force on the other. It is possible to describe the Coulomb interaction via an intermediate step by ...

Electric Fields

Source: Yong P. Chen, PhD, Department of Physics &#38; Astronomy, College of Science, Purdue University, West Lafayette, IN
An electric field is generated ...

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on ...

Source: Yong P. Chen, PhD, Department of Physics &#38; Astronomy, College of Science, Purdue University, West Lafayette, IN
Magnetic fields can be ...

Electric Charge in a Magnetic Field

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment duplicates J.J. Thomson's famous experiment at the end of ...

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 ...

Electromagnetic Fields

Electric fields generated by static charges, often referred to as electrostatic fields, are characteristically different from electric fields created by ...

Magnetic Force

In addition to the electric forces between electric charges, moving electric charges exert magnetic forces on each other. A magnetic field is created by a ...

Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects. [Clarification Statement: Emphasis is on both quantitative and conceptual descriptions of gravitational and electric fields.] [Assessment Boundary: Assessment is limited to systems with two objects.]

HS-PS2-4

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 ...

Electrical Power

Electric power is the product of current and voltage, represented in units of joules per second, or watts. For example, cars often have one or more ...

Using electric appliances for a longer period of time consumes more electrical energy and results in a higher electric bill. The energy produced by the ...

Batteries and Fuel Cells

A battery is a galvanic cell that is used as a source of electrical power for specific applications. Modern batteries exist in a multitude of forms to ...

Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current. [Assessment Boundary: Assessment is limited to designing and conducting investigations with provided materials and tools.]

Electric Charges

From lightning during thunderstorms to electronic devices, the phenomenon of electromagnetism is all around us. The electromagnetic force is one of the ...

electric-field-of-two-equal-and-opposite-charges

Electric Field of Two Equal and Opposite Charges

Atoms generally contain the same number of positively and negatively charged particles, protons, and electrons. Hence, they are electrically neutral. ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

Atomic Structure

All matter is composed of atoms, the smallest individual units of elements. Each atom is made up of three subatomic particles: protons, neutrons, and ...

Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials. [Clarification Statement: Emphasis is on the attractive and repulsive forces that determine the functioning of the material. Examples could include why electrically conductive materials are often made of metal, flexible but durable materials are made up of long chained molecules, and pharmaceuticals are designed to interact with specific receptors.] [Assessment Boundary: Assessment is limited to provided molecular structures of specific designed materials.]

HS-PS2-6

Cutting Electric Bills with Efficient Lighting

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