The electric charge is a fundamental physical property of matter, responsible for creating and sensing the effects of electromagnetic fields. It determines how subatomic particles, such as protons and electrons, interact with each other through the electromagnetic force, one of the four fundamental forces of nature.
Essentially, electric charge is the origin of all electrical phenomena we observe, from a simple static shock to the operation of complex energy systems. Understanding its concept is the first step to mastering electricity and ensuring energy safety and efficiency in any project.
Next, we will discuss everything about the topic, from its origin to its practical applications. Continue reading to deepen your knowledge and understand how this concept connects to the best energy solutions on the market.
Atomic structure and origin of electric charges
All matter is composed of atoms, which have a central nucleus with protons and neutrons, and an external region called the electron cloud, where electrons orbit. The origin of the electric charge lies precisely in the composition of these subatomic particles.
A body is considered electrically neutral when it has the same number of protons and electrons. Electrification occurs when there is an imbalance, that is, a body gains or loses electrons, which are the particles that move between atoms.
Protons, Electrons, and Neutrons
- Protons: located in the nucleus, have a positive electric charge and do not move.
- Electrons: orbit the nucleus, have a negative electric charge and are responsible for electrification when they move.
- Neutrons: reside in the nucleus and have no electric charge, being neutral.
Types of electric charge
There are two types of electric charge in nature: positive and negative.
This sign convention, proposed by Benjamin Franklin, is universally accepted in physics and engineering.
The determination of the type of charge of a body depends on its balance of electrons. A body that loses electrons ends up with a positive charge, while a body that gains electrons becomes negatively charged.
- Positive charge: occurs when an atom or body loses one or more electrons, resulting in more protons than electrons.
- Negative charge: happens when an atom or body gains one or more electrons, creating an excess of negative charge.
Interactions between electric charges
The interaction between charges is determined by a fundamental principle: like charges repel each other, while opposite charges attract each other. This force gives rise to various electrical phenomena.
A common example is when a balloon rubbed on hair sticks to the wall. The electrified balloon attracts opposite charges on the wall’s surface, generating an adhesive force. This same principle is the basis for the operation of motors and generators.
The interaction between electric charges is mainly manifested by two opposing behaviors: attraction and repulsion. These phenomena explain how charges influence each other and are the basis for understanding everything from simple static experiments to the operation of electrical equipment complex.
- Repulsion: two positive charges or two negative charges, when close, exert a force that pushes them apart.
- Attraction: a positive charge and a negative charge, when brought close together, generate a force that unites them.
Unit of electric charge
The standard unit for measuring electric charge in the International System (SI) is the Coulomb (C). It represents the amount of charge that flows through a conductor in one second when the current is one ampere.
The elementary charge (e) is the smallest amount of charge found free in nature. It corresponds to the charge value of a single proton or electron, which is approximately 1.602 x 10⁻¹⁹ C, serving as the basis for all charge calculations.
Elementary charge
The elementary charge (e) is the smallest amount of electric charge that can be found free in nature. It corresponds to the absolute value of the charge of a single proton or a single electron, and its value is approximately 1.602 x 10⁻¹⁹ C.
This means that the charge of any electrified body is always an integer multiple of the elementary charge. It is not possible, for example, to find a body with a charge of 1.5 times the value of e. This concept is the basis of the Charge Quantization Principle.
The only known exception to this rule is quarks, particles that make up protons and neutrons and have fractional charges (+2/3 e or -1/3 e). However, they have never been observed in isolation in nature, always existing in combinations that result in an integer charge.
Fundamental principles of electric charges
Two principles govern the behavior of electric charges: the principle of conservation and the principle of quantization. Understanding these pillars is essential for designing and managing reliable and safe electrical systems, like those developed by Tecnogera.
The Conservation Principle ensures that the total charge in an isolated system is always constant.
The Quantization Principle, on the other hand, establishes that electric charge is always a multiple of a fundamental value, the elementary charge.
Definitions and examples
- Conservation Principle: electric charge cannot be created or destroyed, only transferred from one body to another.
- Quantization Principle: the total charge (Q) of a body is always an integer multiple (n) of the elementary charge (e), according to the formula Q = n • e.
How to calculate electric charge?
The calculation of the electric charge (Q) of a body is done with the formula Q = n • e. This equation allows quantifying the imbalance of electrons in an object, that is, discovering its total charge.
In the formula:
- Q is the total charge.
- n is the number of excess or missing electrons.
- e is the value of the elementary charge (1.602 x 10⁻¹⁹ C).
With this relationship, we can determine the charge of any electrified body.
Advanced formulas and applications
In addition to the basic calculation, the Coulomb’s Law is an advanced formula that describes the interaction force (F) between two point electric charges (q₁ and q₂), separated by a distance (d). This law is fundamental to electrostatics and various technological applications.
The formula is expressed as F = k • |q₁ • q₂| / d², where k is the electrostatic constant of vacuum (≈ 9 x 10⁹ N•m²/C²). It allows calculating the intensity of the attraction or repulsion force between the charges, being essential for the design of electronic components and electrical systems.
Application in systems with multiple charges
To calculate the resultant force on a charge in a system with multiple other charges, the Superposition Principleis applied. The force that each charge exerts individually is calculated, and then all these forces are vectorially summed to find the total force.
Electrification processes
Charge transfer can occur through three processes: friction, contact, and induction. Understanding these methods is vital for safety in industrial environments, where the accumulation of static charge can pose risks.
A good grounding design, for example, is crucial to neutralize charges generated by these processes and ensure the integrity of equipment and people, one of Tecnogera’s specialties in energy solutions.
Processes:
- Frictional electrification: occurs when rubbing two different materials, where one loses electrons and the other gains. Example: combing dry hair.
- Electrification by contact: an electrified body touches a neutral one, transferring part of its charge to it.
- Electrification by induction: an electrified body reorganizes the charges of a nearby neutral body without touching it, and can electrify it if there is grounding.
Conductor vs. electrical insulator
The difference between conductive and insulating materials lies in the ease with which electrons move through them. This property defines the application of each in electrical systems.
Conductors, like metals, have free electrons that move easily, allowing the passage of current. In insulators, like rubber and plastic, electrons are tightly bound, blocking the flow of electricity.
Materials and their applications
- Conductive metals: copper and aluminum are used in wires and cables to efficiently transmit energy.
- Polymeric insulators: rubber and plastic coat wires and components to ensure safety and prevent short circuits.
- Semiconductors: silicon and germanium have controllable conductivity and are the foundation of modern electronics.
Practical applications of electric charges
The principles of electric charge are the basis of numerous technologies, from energy storage in batteries to the operation of touch screens and medical equipment.
In industry, charge control is used in processes like electrostatic automotive painting. In medicine, the electrocardiogram (ECG) measures the heart’s small electrical impulses to diagnose health problems.
Main areas and functional examples:
- Energy storage: batteries and capacitors, essential for uninterruptible power systems and portable devices, work by accumulating electric charges.
- Medical diagnosis: equipment such as ECG and EEG capture the body’s electric fields to monitor health.
- Electronic sensors: cell phone screens, for example, detect the change in an electric field caused by the touch of a finger.
Electric charge and electric current
Charge and electric current are related concepts. The electric current (I) is the orderly flow of electric charges through a conductor, usually electrons, measured in amperes (A).
The relationship is given by the formula I = Q / Δt, where the current is the amount of charge (Q) that passes through a point in a time interval (Δt). Without the movement of charges, there is no current.
To understand the difference, imagine a river: the electric charge would be like the water molecules themselves, the essential raw material. By themselves, they can be stationary.
The electric current, on the other hand, is the flow of this water, that is, the number of molecules passing through a specific point in the river every second. Therefore, the charge is the “what” (the electrons) and the current is the orderly movement of this “what” through a conductor; one does not exist without the other in an active circuit.
Direct and alternating current
- Direct current (DC): the flow of charges occurs in a single direction, as in cells and batteries.
- Alternating current (AC): the direction of the flow periodically reverses. It is the type of current supplied by power companies.
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