18.4 Electric Field: Concept of a Field Revisited
3 min read•june 18, 2024
Electric fields surround charged objects, exerting forces on other charges. These invisible fields are crucial in understanding electrostatic interactions. The strength of an depends on the and distance, following ###'s_Law_0###.
Calculating forces on test charges within electric fields is a key application. By determining field strength and using the equation F = qE, we can predict how charged particles will behave in various electrical scenarios.
Electric Field
Electric field definition and strength
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- Region around a charged object where another charged object experiences an electric
- Vector quantity has both magnitude and direction
- Strength () is the force per unit calculated using
- represents the force
- represents the
- For a point charge, at a distance is given by Coulomb's law:
- is ()
- is the source charge
- is the distance from the source charge to the point of interest
- Direction is radially outward for a positive source charge () and radially inward for a negative source charge ()
- The allows for the calculation of the total electric field from multiple charges by vector addition
Force calculation on test charges
- Force on a within an electric field is calculated using
- is the force
- is the test charge
- is the electric field strength at the location of the test charge
- Direction of the force is the same as the electric field for a positive test charge and opposite for a negative test charge
- Steps to find the force:
- Determine the electric field strength at the location of the test charge using the appropriate equation (Coulomb's law for a point charge)
- Multiply the electric field strength by the magnitude of the test charge to find the force
- Electric dipoles (such as water molecules) experience both a net force and a torque in non-uniform electric fields
Relationship of field strength to force
- Electric field strength is directly proportional to the force experienced by a charged particle
- Stronger electric field results in a greater force on a charged particle
- Force on a charged particle is the product of the electric field strength and the particle's charge ()
- If the electric field strength doubles, the force on a charged particle will also double, assuming the charge remains constant
- Direction of the force on a charged particle depends on both the direction of the electric field and the sign of the particle's charge
- Positive charge (proton) experiences a force in the same direction as the electric field
- Negative charge (electron) experiences a force in the opposite direction of the electric field
Field Visualization and Properties
- Electric are used to visualize the direction and strength of electric fields
- Equipotential surfaces are regions where the electric is constant, and are always perpendicular to electric field lines
- measures the flow of the electric field through a given surface area
- describe the fundamental behavior of electric and magnetic fields, including their interactions and propagation
Key Terms to Review (32)
Adhesive forces: Adhesive forces are the attractive forces between unlike molecules. They play a significant role in phenomena such as capillary action and the wetting of surfaces.
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.
Charge: Charge is a fundamental property of matter that is the source of all electrical phenomena. It is the basic unit of electrical charge that can be either positive or negative and is responsible for the creation of electric fields and the flow of electric current.
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 Constant: Coulomb's constant, also known as the electrostatic constant, is a fundamental physical constant that represents the strength of the electrostatic force between two point charges. It is a crucial parameter in understanding and describing various electromagnetic phenomena, including Coulomb's law, electric fields, and electrical potential.
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.
Electric charge: Electric charge is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field. Charges are either positive or negative and are measured in coulombs (C).
Electric Dipole: An electric dipole is a separation of positive and negative electric charges within a system, typically a pair of equal and opposite charges separated by a small distance. This separation of charges creates an electric field and potential that are fundamental to understanding various phenomena in electromagnetism.
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 field strength: Electric field strength is a measure of the force experienced by a unit positive charge placed in an electric field. It is represented by the symbol $E$ and is measured in volts per meter (V/m).
Electric Flux: Electric flux is a measure of the total electric field passing through a given surface. It represents the number of electric field lines that intersect a surface, providing a quantitative way to describe the electric field in a specific region of space.
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.
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.
Equipotential Surface: An equipotential surface is a surface in an electric field where the electric potential is constant. In other words, all points on an equipotential surface have the same electric potential value.
Field Lines: Field lines are imaginary lines that represent the direction and strength of a field, such as an electric or magnetic field. They provide a visual representation of the field and help in understanding the properties and behavior of the field.
Force: Force is a vector quantity that represents the interaction between two objects, causing a change in the motion or shape of one or both objects. It is a fundamental concept in physics that describes the push or pull experienced by an object due to the influence of another object or system.
Force field: A force field is a region of space in which an object experiences a non-contact force. Examples include gravitational fields, electric fields, and magnetic fields.
Gauss's Law: Gauss's law is a fundamental principle in electromagnetism that relates the electric flux through a closed surface to the total electric charge enclosed within that surface. It provides a way to calculate the electric field based on the distribution of electric charges.
Maxwell's Equations: Maxwell's equations are a set of four fundamental equations that describe the relationships between electric and magnetic fields and electric charges and currents. These equations form the foundation of classical electromagnetism and are essential for understanding various electromagnetic phenomena.
Permittivity: Permittivity is a measure of the ability of a material to store electric energy in an electric field. It is a fundamental property that describes how an electric field affects, and is affected by, a dielectric medium. Permittivity is a crucial concept in understanding the behavior of electric fields, energy storage in capacitors, and the propagation of electromagnetic waves.
Potential: Potential refers to the ability or capacity to do work or cause change. In the context of physics, potential is a scalar field that describes the potential energy per unit charge at a given point in space, which determines the force that would be exerted on a charged particle placed at that location.
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.
Scalar Field: A scalar field is a mathematical function that assigns a scalar value to every point in a space. In the context of physics, a scalar field is a physical quantity that has a value associated with every point in space, with no direction associated with it.
Source Charge: A source charge is an electric charge that is responsible for creating an electric field in the surrounding space. It is the origin or starting point of the electric field, and its presence influences the behavior and distribution of other charges within the field.
Superposition Principle: The superposition principle states that when two or more waves or fields interact, the resulting wave or field is the vector sum of the individual waves or fields. This principle applies to various physical phenomena, including sound interference, electric fields, and electrical potential.
Test charge: A test charge is a hypothetical charge with negligible magnitude used to measure the electric field strength at a point without disturbing the field itself. It is typically positive and small enough not to influence nearby charges or fields.
Test Charge: A test charge is a small, hypothetical electric charge that is used to probe and measure the electric field at a particular point in space. It is a fundamental concept in the study of electrostatics and is essential for understanding the behavior of electric fields.
Vector Field: A vector field is a function that assigns a vector to every point in a given space, typically a two-dimensional or three-dimensional space. It is a mathematical representation of a physical quantity that has both magnitude and direction, such as an electric or gravitational field.
Volt: A volt is the unit of electric potential difference, which measures the amount of electric potential energy per unit charge between two points in an electric circuit. It helps us understand how much energy is available to move electric charges through a conductor, connecting it to concepts like power, energy storage, and circuit behavior.