18.1 Static Electricity and Charge: Conservation of Charge
3 min read•june 18, 2024
Electric charge is a fundamental property of matter that determines how objects interact electromagnetically. Positive and negative charges attract each other, while like charges repel. This principle governs everything from to the behavior of subatomic particles.
is a key law in physics, stating that the total charge in a closed system remains constant. This concept explains phenomena like static electricity and electric currents, and it's crucial for understanding how charges interact and transfer in various situations.
Electric Charge and Interactions
Electric charge interactions
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- Electric charge fundamental property of matter determines electromagnetic interactions
- Two types of electric charge: positive (protons) and negative (electrons)
- Like charges repel each other (positive repels positive, negative repels negative)
- Opposite charges attract each other (positive attracts negative, negative attracts positive)
- Protons have a positive charge, electrons have a negative charge
- Protons and electrons have equal magnitude of charge but opposite signs
- Neutral objects have an equal number of protons and electrons resulting in no net charge
- Charged objects have an imbalance of protons and electrons
- Positively charged objects have more protons than electrons (net positive charge)
- Negatively charged objects have more electrons than protons (net negative charge)
- ###'s_Law_0### describes the force between two charged objects
- , where is the force, is Coulomb's constant, and are the charges, and is the distance between the charges
- Force directly proportional to product of charges and inversely proportional to square of distance between them
- Larger charges and smaller distances result in stronger forces
Examples of static electricity
- Rubbing a balloon on hair transfers electrons from hair to balloon
- Balloon gains negative charge from electrons transferred from hair
- Walking across a carpet and touching a metal doorknob
- Body accumulates charge from friction with carpet, discharges to doorknob (sparks)
- Removing a sweater or shirt causes static cling
- Friction between clothing and body can cause garments to stick together
- Combing hair with a plastic comb
- Comb gains negative charge from electrons transferred from hair (hair stands up)
- Rubbing a glass rod with a silk cloth
- Glass rod gains positive charge, silk cloth gains negative charge (rod attracts small pieces of paper)
Conservation of charge law
- states net charge in isolated system remains constant
- Charge cannot be created or destroyed, only transferred or redistributed
- In a closed system, total positive charge must equal total negative charge
- When two objects are rubbed together, they transfer charges but total charge remains the same
- One object gains the same amount of charge that the other object loses (conservation of charge)
- In any charge interaction or chemical reaction, total charge before and after event remains the same
- Example: In a battery, chemical reactions transfer charges but total charge is conserved
- Law of conservation of charge is a fundamental principle in physics and chemistry
- Helps explain various phenomena (static electricity, electric current, chemical bonding)
- Charge conservation essential for understanding behavior of charged particles and electromagnetic interactions
Electric Fields and Related Concepts
- : region around a charged object where electric forces are exerted on other charges
- Represented by field lines showing direction and strength of electric force
- : potential energy per unit charge at a point in an electric field
- Measured in volts, determines the work needed to move a charge in the field
- : alignment of electric dipoles in a material due to an external electric field
- Occurs in dielectrics, materials that can be polarized but don't conduct electricity well
- Insulators: materials that resist the flow of electric charge (e.g., rubber, glass)
- Play important role in controlling and isolating electric charges in various applications
Key Terms to Review (33)
Antielectron: An antielectron, also known as a positron, is the antimatter counterpart of an electron. It has the same mass as an electron but carries a positive charge.
Charles-Augustin de Coulomb: Charles-Augustin de Coulomb was a French physicist who is best known for his work on the fundamental laws of electrostatic attraction and repulsion, which are now known as Coulomb's law. His research laid the foundation for our understanding of static electricity and charge interactions.
Conduction: Conduction is the transfer of heat through a material without the involvement of any bulk motion of the material. It occurs when heat flows from a region of higher temperature to a region of lower temperature within a material or between materials in direct contact, without any displacement of the material itself.
Conductivity: Conductivity is a measure of a material's ability to allow the flow of electric current. It is a fundamental property that determines how easily electrons can move through a substance, and it plays a crucial role in understanding various electrical phenomena and applications.
Conservation of Charge: Conservation of charge is a fundamental principle in physics which states that the total electric charge in an isolated system remains constant. It is neither created nor destroyed, but can only be transformed or transferred from one location to another.
Coulomb: Coulomb is the fundamental unit of electric charge, named after the French physicist Charles-Augustin de Coulomb. It is a measure of the amount of electric charge and is a crucial concept in understanding various topics in electricity and magnetism, such as static electricity, electric fields, electric potential, and the behavior of charged particles.
Coulomb force: Coulomb force, also known as the electrostatic force, is the force of attraction or repulsion between two charged particles. It follows an inverse-square law and is governed by Coulomb's law.
Coulomb's Law: Coulomb's law is a fundamental principle in electrostatics that describes the force of interaction between two stationary electric charges. It establishes a mathematical relationship between the magnitude of the electrostatic force, the charges involved, and the distance between them.
Dielectric: A dielectric is an insulating material that increases the storage capacity of a capacitor by reducing the electric field within it. Dielectrics are characterized by their ability to be polarized in the presence of an electric field.
Dielectric: A dielectric is an electrical insulator that can be polarized by an applied electric field. It is a material that does not conduct electric current under normal conditions, but it can support an electrostatic field by storing energy in the form of an electric field. Dielectrics play a crucial role in various topics related to electrostatics and capacitors.
Direction of polarization: Direction of polarization refers to the orientation of the electric field vector in an electromagnetic wave. It describes how the electric field oscillates as the wave propagates.
Electric Field: The electric field is a vector field that describes the force experienced by a stationary, positive test charge at any given point in space. It represents the strength and direction of the electric force exerted on a charged particle by other charges in the vicinity, and is a fundamental concept in the study of electromagnetism and the behavior of charged particles.
Electric potential: Electric potential is the amount of electric potential energy per unit charge at a point in an electric field. It is measured in volts (V).
Electric Potential: Electric potential is the amount of work required to move a unit positive charge from an infinite distance to a specific point in an electric field. It represents the potential energy per unit charge at a given location and is a scalar quantity, meaning it has magnitude but no direction.
Electron: An electron is a fundamental subatomic particle that carries a negative electric charge and is found in all atoms, playing a crucial role in various physical and chemical phenomena. Electrons are responsible for the flow of electric current, the formation of chemical bonds, and the behavior of matter at the atomic and molecular levels.
The concept of the electron is central to understanding topics such as static electricity, electric fields, magnetic fields, the photoelectric effect, quantum mechanics, and the structure of atoms. Electrons are the building blocks of matter and are essential for understanding the fundamental nature of the universe.
Electroscope: An electroscope is a device used to detect and measure the presence of electric charge. It consists of a metal case with a metal leaf or foil suspended inside, which moves in response to the presence of an electric charge.
Electrostatic force: Electrostatic force is the force of attraction or repulsion between two charged objects. It operates according to Coulomb's Law, which quantifies the magnitude of this force.
Electrostatic Force: Electrostatic force is the attractive or repulsive force that exists between electrically charged particles or objects. It is a fundamental force in nature that governs the behavior of static electricity and the interactions between charged entities.
Induction: Induction is the process by which an electric charge or current can create a magnetic field or induce an electromotive force (EMF) in a nearby conductor without direct contact. It is a fundamental concept in electromagnetism that describes the relationship between electric and magnetic fields.
Insulator: An insulator is a material that does not conduct electricity or heat well, making it essential for preventing energy loss and maintaining safety in electrical systems. Insulators resist the flow of electric current and thermal energy, which is crucial for a variety of applications ranging from household appliances to high-voltage power lines. Their ability to inhibit the transfer of energy helps maintain controlled environments and protects sensitive components from damage.
Law of conservation of charge: The law of conservation of charge states that the total electric charge in an isolated system remains constant regardless of any internal changes. This principle implies that charge can neither be created nor destroyed, only transferred from one part of the system to another.
Neutron: A neutron is a subatomic particle found in the nucleus of an atom, possessing no electric charge and a mass slightly greater than that of a proton. Neutrons play a crucial role in the stability of atomic nuclei.
Neutron: A neutron is a subatomic particle that has no electric charge and is found in the nucleus of an atom, along with protons. Neutrons play a crucial role in the stability and properties of atomic nuclei, as well as in various physical and nuclear processes.
Polarization: Polarization is a fundamental property of electromagnetic waves, including light, that describes the orientation of the electric field oscillations within the wave. It is a crucial concept that underlies many important phenomena in the fields of static electricity, electromagnetism, and optics.
Proton: A proton is a subatomic particle that is the positively charged constituent of the nucleus of an atom, with a mass approximately 1,836 times that of an electron. Protons are fundamental to understanding various topics in physics, including static electricity, electric fields, magnetic fields, atomic structure, and nuclear physics.
Proton-proton cycle: The proton-proton cycle is a series of nuclear fusion reactions that convert hydrogen into helium, releasing energy. It is the dominant energy source in stars like the Sun.
Resistivity: Resistivity is a measure of how strongly a material opposes the flow of electric current. It is denoted by the Greek letter $\rho$ (rho) and has units of ohm-meters ($\Omega \cdot m$).
Resistivity: Resistivity is a fundamental property of materials that measures their ability to resist the flow of electric current. It is a measure of how strongly a material opposes the passage of electric charge, and it is a crucial factor in understanding the behavior of electrical circuits and the design of electrical components.
Static Electricity: Static electricity refers to the buildup of electrical charges on the surface of an object, resulting from the imbalance of positive and negative charges. It is a fundamental concept in the study of electricity and is closely related to the principle of conservation of charge.
Thermal conductivity: Thermal conductivity is a material's ability to conduct heat. It measures the rate at which heat energy passes through a material.
Triboelectric Effect: The triboelectric effect is the buildup of static electricity that occurs when two different materials are brought into contact and then separated. This process creates an imbalance of electric charge, with one material becoming positively charged and the other negatively charged.
Van de Graaff Generator: The Van de Graaff generator is a device that uses static electricity to produce extremely high voltages, often reaching millions of volts. It is primarily used for demonstrations and research in the fields of electrostatics and atomic physics.
Van de Graaff generators: A Van de Graaff generator is a device that uses a moving belt to accumulate electric charge on a hollow metal globe, creating high voltages. It is commonly used in physics demonstrations to illustrate electrostatic principles.