Name: electric charge in circuits
Uploaded: 2024-04-11T12:48:28.000Z
Duration: 1 min 14 s
Channel: JoVE

K12 Standards

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

High School

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

HS-PS2-5

Charge and Current

Charge, an inherent property of matter, is responsible for a wide range of electric phenomena. The SI unit of charge is the coulomb.
All matter comprises atoms, which consist of three subatomic particles: protons, neutrons, and electrons. When the number of protons and electrons are the same, the atom is electrically neutral.
Charges can be transferred from one body to another, and the net charge within the system remains the same.
Charges are quantized, meaning the charge on a body is always the integral multiple of the electronic charge.
When a conducting wire is connected to a battery, the movement of charges within the wire creates current. Current is the time rate of flow of electric charge, measured in amperes.
Conventionally, its direction is considered opposite to the flow of negative charges.

The charge transferred over a specific time interval can be obtained by integrating the current with respect to time.
There are two most common types of currents. A direct current remains constant with time, while the alternating current varies sinusoidally with time.

charge and current

Electric charge is the most fundamental quantity in an electric circuit. The effects of electric charge are encountered daily, such as when a wool sweater sticks to the human body or when a person receives a shock while walking on a carpet.
Charge is an inherent property of the atomic particles that make up matter and is measured in units called coulombs (C). Matter is composed of atoms, each consisting of electrons, protons, and neutrons. Electrons have a negative charge (-e), while protons carry a positive charge (+e), with both charges having the same magnitude. An atom is electrically neutral when it has an equal number of protons and electrons.
Key points about electric charge include:
<ul>
	<li>&#8226; The coulomb (C) is a relatively large unit for measuring charges, and practical charge values are often in picocoulombs (pC), nanocoulombs (nC), or microcoulombs (&#956;C).</li>
	<li>&#8226; Observations reveal that natural charges exist only as integral multiples of the elementary charge (e), the charge carried by an electron or proton.</li>
	<li>&#8226; The law of conservation of charge asserts that electric charge cannot be created nor destroyed; it can only be transferred. As a result, the total electric charge in a system remains constant. Charge can be moved from one place to another and converted into different forms of energy.</li>
</ul>
The movement of positive charges in one direction and negative charges in the opposite direction gives rise to electric current. Typically, a conventional current flow is defined as the movement of positive charges, and it is measured in units known as amperes (A). When the current remains constant over time, it is called direct current (DC). In cases where the current varies with time, it is denoted as a time-varying current, often referred to as alternating current (AC). AC is commonly used in households to power appliances like air conditioners, refrigerators, and washing machines.

Charge, an inherent property of matter, is responsible for a wide range of electric phenomena. The SI unit of charge is the coulomb.
All matter comprises ...

Education

JoVE Core

Electrical Engineering

Unit 1

Basics of Electric Circuits

KEY TERMS AND CONCEPTS

electric charge in circuits

Electric charge in circuits explains how charged particles behave in matter and how current is produced. Everyday static effects, like a wool sweater sticking to the body or a shock from a carpet, show charge in action. Charge is an inherent property of atomic particles and is measured in coulombs (C).

Matter is made of atoms with electrons, protons, and neutrons. Electrons carry a negative charge (-e), and protons carry a positive charge (+e). These two charges have the same magnitude. An atom is electrically neutral when it has equal numbers of protons and electrons.

The coulomb is a large unit for many practical situations. Smaller charges are often described in picocoulombs (pC), nanocoulombs (nC), or microcoulombs (μC). Observations also show that natural charges appear only as integral multiples of the elementary charge (e), which is the charge of an electron or proton.

Electric charge follows the law of conservation of charge. Charge cannot be created or destroyed. It can only be transferred, so the total charge in a system stays constant. When positive charges move one way and negative charges move the opposite way, electric current is produced.

Conventional current means the flow of positive charge and is measured in amperes (A). If the current stays constant over time, it is called direct current, or DC. If the current changes with time, it is called time-varying current, often called alternating current, or AC. AC is commonly used in homes to power appliances such as air conditioners, refrigerators, and washing machines.

Electric Charge in Circuits

Electric charge in circuits explains how charged particles behave in matter and how current is produced. Everyday static effects, like a wool sweater sticking to the body or a shock from a carpet, show charge in action. Charge is an inherent property of atomic particles and is measured in coulombs (C). Matter is made of atoms with electrons, protons, and neutrons. Electrons carry a negative charge (-e), and protons carry a positive charge (+e). These two charges have the same magnitude. An...

voltage

Voltage in Electric Circuits

Voltage in electric circuits is the energy needed to move electric charge between two points. It is also called electromotive force, or EMF. In most circuits, an external force such as a battery provides this energy for electron movement in a conductor. The voltage between points a and b is written as v_ab. It is defined as the work, or energy, needed to move a unit charge from point a to point b. In the equation, w is the energy in joules and q is the charge in coulombs. Voltage is measured...

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...

electric circuit elements

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,...

independent and dependent sources

Circuit Source Symbols and Controls

Circuit sources in electrical circuits can be independent or dependent. They provide the power a circuit needs to operate. Independent voltage sources supply a fixed voltage, and independent current sources supply a fixed current. Their output does not change because of other parts in the circuit. These sources use standard symbols in circuit diagrams. An independent voltage source is shown with + and - signs to mark the potential difference. An independent current source is shown with an...

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

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,...

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 electric charge, the elementary charge, and current work in circuits, including DC and AC, with real examples from everyday life.

Electric Charge in Circuits | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

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 ...

Force and Acceleration

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

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 ...

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

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

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 Angular Momentum

A system&#39;s total angular momentum remains constant if the net external torque acting on the system is zero. Considering a system that consists of n ...

conservation-of-angular-momentum-application

Conservation of Angular Momentum: Application

A system&#39;s total angular momentum remains constant if the net external torque acting on the system is zero. Examples of such systems include a freely ...

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

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 ...

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 ...

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 ...

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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 ...

gravitation-between-spherically-symmetric-masses

Gravitation Between Spherically Symmetric Masses

The gravitational potential energy between two spherically symmetric bodies can be calculated from the masses and the distance between the bodies, ...

/files/media/science-education/science-education-thumbs/14717.jpg

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 ...

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 ...

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

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 ...

Electromagnetic Fields

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

Maxwell's Equation Of Electromagnetism

James Clerk Maxwell (1831&#x2013;1879) was one of the major contributors to physics in the nineteenth century. Although he died young, he made major ...

Symmetry in Maxwell's Equations

Once the fields have been calculated using Maxwell&#x27;s four equations, the Lorentz force equation gives the force that the fields exert on a charged ...

Induction

An emf is induced when the magnetic field in a coil is changed by pushing a bar magnet into or out of the coil. emfs of opposite signs are produced by ...

Faraday's Law

Faraday&#39;s law state that the induced emf is the negative change in the magnetic flux per unit of time. Any change in the magnetic field or change in ...

Lenz's Law

The direction in which the induced emf drives the current around a wire loop can be found through the negative sign. However, it is usually easier to ...

Ohm's Law

Resistors, often made from metallic alloys or carbon compounds, model a material&#x27;s current-resisting behavior.
Ohm&#x27;s law states that the voltage ...

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.

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

Band Theory

When two or more atoms come together to form a molecule, their atomic orbitals combine and molecular orbitals of distinct energies result. In a solid, ...

Semiconductors

Materials are broadly categorized into three types as metals, insulators, and semiconductors.
Metals have no energy band gap due to the overlap of the ...

Conductors and Insulators

Some materials may easily let electrical charges pass through them, while others obstruct their flow. The former are called conductors and the latter ...

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

Electric Charge in Circuits

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