Wiktor Wise
Electricity is a form of energy that can be carried by wires and is used for heating, lighting, and powering machines. It is a set of physical phenomena associated with the presence and motion of matter possessing an electric charge. The particle involved in electricity is the electron, which carries a negative charge. The presence of either a positive or negative electric charge produces an electric field, and the motion of electric charges creates an electric current and a magnetic field. The study of electricity has a long history, with ancient cultures observing and experimenting with electric fish and objects like amber. Over time, scientists such as Luigi Galvani, Alessandro Volta, Hans Christian Ørsted, André-Marie Ampère, Michael Faraday, Georg Ohm, and James Clerk Maxwell made significant contributions to our understanding of electricity and its relationship with magnetism.
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Electric charge
Electricity is a phenomenon associated with stationary or moving electric charges. Electric charge is a fundamental property of matter and is borne by elementary particles. It is the cornerstone of comprehending the physical world.
The SI derived unit of electric charge is the coulomb (C), named after French physicist Charles-Augustin de Coulomb. In electrical engineering, it is also common to use the ampere-hour (A·h). In physics and chemistry, it is common to use the elementary charge (e) as a unit. Chemistry also uses the Faraday constant, which is the charge of one mole of elementary charges.
There are two types of electric charges: positive and negative. Positive charges are associated with protons, which are subatomic particles residing in the nucleus of an atom. They are represented by the symbol '+'. On the other hand, negative charges are linked to electrons, which orbit the atomic nucleus and are denoted by the symbol '–'. The distinction between positive and negative charges is vital to understanding the behaviour of electrically charged objects. Opposite charges, such as positive and negative, attract each other, while like charges repel each other.
The total electric charge of an isolated system remains constant, regardless of changes within the system. This law is inherent to all processes known to physics. The conservation of charge results in the charge-current continuity equation. The rate of change in charge density ρ within a volume of integration V is equal to the area integral over the current density J through the closed surface S = ∂V, which is, in turn, equal to the net current I. This implies that charge can neither be created nor destroyed but can be transferred from one body to another by certain methods like conduction and induction.
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Electric fields
Electricity is a set of physical phenomena associated with the presence and motion of matter with an electric charge. Electric charge is a fundamental property of matter and is carried by elementary particles. In most applications, Coulomb's law determines the force acting on an electric charge.
An electric field is a physical field that surrounds electrically charged particles such as electrons. It is a vector field that describes the capacity of a single or group of charges to exert attractive or repulsive forces on another charged object. The electric field is stronger nearer charged objects and weaker further away.
The SI unit for the electric field is the volt per meter (V/m), which is equal to the newton per coulomb (N/C). The magnitude and direction of the electric field are expressed by the value of E, called electric field strength or electric field intensity. The strength of an electric field E at any point may be defined as the electric, or Coulomb, force F exerted per unit positive electric charge q at that point, or simply E = F/q. The direction of the force that is exerted on a negative charge is opposite to that exerted on a positive charge.
The study of electric fields created by stationary charges is called electrostatics. Faraday's law describes the relationship between a time-varying magnetic field and the electric field. The electric field is important in many areas of physics and is exploited in electrical technology.
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Electrostatics
Electricity is a phenomenon associated with stationary or moving electric charges. The particle involved in electricity is the electron, which carries a negative charge. The various manifestations of electricity are the result of the accumulation or motion of electrons.
Protons and electrons have the same amount of charge. When they are in close proximity, they nullify each other's charge, resulting in an electrically neutral combination. Most bodies are composed of equal amounts of positive and negative charges, leading to a small or zero net electrical interaction. However, when charges are transferred between bodies, it creates the familiar phenomenon of static electricity or electrostatics.
The study of electrostatics has led to the development of various mathematical methods and equations, such as Poisson's equation and Laplace's equation, which help calculate electric fields, charge distributions, and electric potential based on known configurations of charges, conductors, and insulators. These calculations are essential for understanding the behaviour of charges in electrostatic scenarios.
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Electromagnetism
Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is closely related to magnetism, with both being part of the phenomenon of electromagnetism. Electromagnetism is, fundamentally, the interaction that occurs between particles with electric charge via electromagnetic fields.
The electromagnetic force is one of the four fundamental forces of nature, and is the dominant force in the interactions of atoms and molecules. It can be thought of as a combination of electrostatics and magnetism, which are distinct but intertwined phenomena. Electric forces cause an attraction between particles with opposite charges and a repulsion between particles with the same charge. Meanwhile, magnetism is an interaction that occurs between charged particles in relative motion.
The ancient Chinese, Mayan, and potentially Egyptian civilizations knew that the naturally magnetic mineral magnetite had attractive properties. Ancient people were also aware of lightning and static electricity, though they did not understand the mechanisms behind them. In the 18th and 19th centuries, scientists and mathematicians such as Coulomb, Gauss, and Faraday developed namesake laws that helped explain the formation and interaction of electromagnetic fields. This culminated in the 1860s with the discovery of Maxwell's equations, which provided a complete description of classical electromagnetic fields.
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Current flow
In conductive materials, such as metals, certain electrons are not bound to any particular atom and are free to move about. These free electrons move from areas of negative charge to areas of positive charge, creating an electric current. A complete path, or circuit, is required for electrons to flow. This circuit must lead from the negative charge source, through the conductor, and back to the positive charge source. The circuit forms a closed, conducting loop through which electrons can flow, providing energy to any device connected to it.
The direction of conventional current is defined as the direction in which positive charges flow. However, in metal wires and many other electronic circuit components, the charge carriers are negatively charged electrons, which flow in the opposite direction of conventional current. This discrepancy arose because the convention was created before scientists knew that electrons were the charges actually moving.
The flow of current can be direct current (DC), where the movement of electric charge occurs in only one direction, or alternating current, where the direction of flow reverses at regular intervals. Direct current is produced by sources such as batteries, solar cells, and electric machines of the dynamo type. Alternating current is commonly found in household electrical receptacles. Direct current may flow through conductors such as wires, semiconductors, insulators, or even through a vacuum.
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Frequently asked questions
Electricity is a form of energy that can be carried by wires and is used for heating, lighting, and providing power for machines. It is a set of physical phenomena associated with the presence and motion of matter possessing an electric charge.
An electric charge is a fundamental property of matter and is carried by elementary particles. The particle involved in electricity is the electron, which carries a negative charge. Protons have a positive charge, and the force of attraction between protons and electrons in an atom's nucleus creates balance.
Electricity is created by the accumulation or motion of electrons. Electrons can be pushed out of their orbits in an atom's outermost shells and shifted from one atom to another, creating a current.
An electric current is the movement of electric charges, which can be in the form of negatively charged electrons or positively charged electron deficiencies called "holes". The motion of electric charges creates a magnetic field and is used to power electrical equipment.
Common phenomena associated with electricity include lightning, static electricity, electric heating, and electric discharges. Lightning, for example, is a form of electricity where electrons move between clouds or from a cloud to the ground, creating a bright flash of light.
