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Electric dipoles are fundamental to understanding distribution in molecules and materials. They arise from the separation of positive and negative charges, creating a that interacts with electric fields.

Permanent dipoles exist in asymmetric molecules like water, while induced dipoles form in neutral atoms exposed to external fields. These concepts are crucial for grasping how materials respond to electric fields and interact with each other.

Electric Dipoles

Permanent electric dipoles in molecules

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Top images from around the web for Permanent electric dipoles in molecules

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  • System with two equal and opposite charges separated by a fixed distance charges not free to move independently
  • (p⃗\vec{p}) vector quantity characterizes strength and orientation of dipole p⃗=qd⃗\vec{p} = q\vec{d}, qq magnitude of each charge, d⃗\vec{d} from negative to positive charge
  • Many molecules have due to asymmetric structure and
    • In water, oxygen atom attracts electrons more strongly than hydrogen atoms creates charge separation
    • Bent geometry of water molecule results in net dipole moment
  • plays a crucial role in determining the presence and strength of permanent dipoles

Formation of induced electric dipoles

  • Induced occurs when neutral atom or molecule subjected to external electric field causes redistribution of electron cloud creates charge separation
  • Positive charges (nuclei) slightly displaced in direction of electric field, negative charges (electrons) displaced in opposite direction
  • Magnitude of moment depends on strength of external electric field and of atom or molecule polarizability measures how easily electron cloud can be distorted by external field
  • Induced dipoles are temporary exist only in presence of external electric field
  • Polarization occurs when many molecules in a material align their dipoles in response to an external electric field

Calculation of electric dipole moment

  • moment (p⃗\vec{p}) calculated using formula p⃗=qd⃗\vec{p} = q\vec{d}
    • qq magnitude of each charge in dipole
    • d⃗\vec{d} displacement vector from negative to positive charge
  • SI unit for electric dipole moment (C·m)
  • Larger dipole moment indicates stronger charge separation more significant effect on surrounding electric field
  • (UU) of electric dipole in external electric field (E⃗\vec{E}) given by U=−p⃗⋅E⃗U = -\vec{p} \cdot \vec{E} dipole tends to align itself with electric field to minimize potential energy
  • (τ⃗\vec{\tau}) experienced by electric dipole in external electric field given by τ⃗=p⃗×E⃗\vec{\tau} = \vec{p} \times \vec{E} causes dipole to rotate and align with field

Behavior of dipoles in electric fields

  • In , electric dipole experiences only torque no net force
    • Torque causes dipole to rotate and align with field
    • Once aligned, dipole remains in stable equilibrium
  • In , electric dipole experiences both torque and net force
    • Net force directed towards region of higher electric field strength
    • Phenomenon known as
  • Force on electric dipole in non-uniform electric field given by F⃗=(p⃗⋅∇)E⃗\vec{F} = (\vec{p} \cdot \nabla)\vec{E}
    • ∇\nabla represents rate of change of electric field in space
  • Behavior of electric dipoles in non-uniform fields basis for various applications in microfluidics and particle manipulation

Dipoles in materials and electrostatics

  • Dielectric constant measures a material's ability to store electrical energy in an electric field, related to its molecular dipole properties
  • studies the behavior of stationary electric charges and fields, including the effects of electric dipoles
  • occur between molecules with permanent or induced dipoles, influencing material properties and behavior

Key Terms to Review (25)

Ammonia (NH3): Ammonia (NH3) is a colorless gas with a distinct, pungent smell that plays an important role in various chemical processes and is commonly used in fertilizers. As a polar molecule, it has a significant dipole moment due to the difference in electronegativity between nitrogen and hydrogen, leading to strong hydrogen bonding. This dipole moment is crucial in understanding how ammonia interacts with other molecules, particularly in the context of electric dipoles.
Charge: Charge is a fundamental property of matter that is the source of all electrical phenomena. It is a scalar quantity that can be positive or negative and is the basis for the attractive and repulsive forces between objects, as well as the flow of electric current.
Coulomb-meter: A coulomb-meter is a device used to measure the electric charge, specifically the amount of electric charge that passes through a given cross-section of an electric circuit. It is a fundamental tool in the study of electric dipoles, which are essential concepts in understanding the behavior of charged particles and the interactions between them.
Dielectrophoresis: Dielectrophoresis is the motion of polarizable particles in a non-uniform electric field. It is a phenomenon where neutral particles experience a net force in the presence of a spatially varying electric field, leading to their movement and potential separation based on their dielectric properties.
Dielectrophoretic Effect: The dielectrophoretic effect refers to the motion of polarized particles or molecules in a non-uniform electric field. It occurs when a dielectric particle, which has no net charge, experiences a force due to the spatial variation of the electric field, causing it to move either towards or away from the region of higher field strength.
Dipole moment: A dipole moment is a measure of the separation of positive and negative electrical charges within a system, indicating the polarity of a molecule. It is represented as a vector quantity with both magnitude and direction.
Dipole Moment: The dipole moment is a measure of the separation of positive and negative electrical charges within a molecule or system. It is a vector quantity that describes the magnitude and direction of the charge separation, and it plays a crucial role in understanding the behavior of electric fields, electric potential, and the properties of dielectric materials.
Dipole-Dipole Interactions: Dipole-dipole interactions are a type of intermolecular force that occurs between polar molecules, where the partially positive end of one molecule is attracted to the partially negative end of another molecule. These interactions play a crucial role in the behavior and properties of many chemical and biological systems.
Displacement Vector: A displacement vector is a mathematical representation of the change in position of an object or particle. It describes the distance and direction of the movement from an initial position to a final position, without regard for the path taken.
Electric dipole: An electric dipole consists of two equal and opposite charges separated by a small distance. It creates an electric field and has a dipole moment, which is a vector quantity pointing from the negative to the positive charge.
Electric Dipole: An electric dipole is a pair of equal and opposite electric charges separated by a small distance. It is a fundamental concept in electrostatics that describes the electric field and potential created by a pair of equal but opposite charges.
Electrostatics: Electrostatics is the branch of physics that studies electric charges at rest. It involves understanding the forces, fields, and potentials associated with static electric charges.
Electrostatics: Electrostatics is the study of electric fields and charges at rest. It encompasses the principles and laws governing the behavior of stationary electric charges and the electric fields they produce. This field of physics is foundational to understanding the interactions between charged particles and the properties of electric fields.
Gradient Operator: The gradient operator is a mathematical tool used to describe the rate of change of a scalar field in the direction of the greatest increase. It is a vector field that points in the direction of the maximum rate of increase of the scalar field and has a magnitude equal to the maximum rate of change.
Induced dipole: An induced dipole is a temporary separation of charge in an otherwise neutral atom or molecule due to the presence of a nearby charge. This phenomenon occurs when an external electric field distorts the electron cloud, creating a dipole moment.
Induced electric dipoles: Induced electric dipoles occur when an external electric field causes a redistribution of charges within an atom or a molecule, leading to a temporary separation of positive and negative charges. This phenomenon results in a dipole moment that aligns with the external field, allowing the atom or molecule to interact with the field and other charged entities. Induced dipoles play a crucial role in various physical processes, including intermolecular interactions and polarization effects.
Molecular Geometry: Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. It is a crucial concept in understanding the physical and chemical properties of molecules, including their polarity and reactivity.
Non-uniform electric field: A non-uniform electric field is one where the strength and direction of the electric field vary with position. This means that as you move through the field, the force experienced by a charged particle changes, leading to more complex interactions compared to a uniform electric field. Non-uniform electric fields are particularly important when studying electric dipoles and calculating electric flux, as they influence how charges behave and how fields interact with surfaces.
Permanent dipole: A permanent dipole is a pair of equal and opposite electric charges separated by a fixed distance, resulting in a constant electric dipole moment. Permanent dipoles occur in molecules where there is an inherent separation of charge due to differences in electronegativity between bonded atoms.
Permanent Electric Dipoles: Permanent electric dipoles are systems where there is a separation of positive and negative charges, creating a stable electric dipole moment that does not change over time. These dipoles result from the arrangement of atoms or molecules that have permanent partial charges due to differences in electronegativity, leading to an asymmetrical distribution of electron density. The presence of permanent dipoles plays a crucial role in understanding molecular interactions, bonding, and the behavior of materials in electric fields.
Polarizability: Polarizability is a measure of how easily the electrons in an atom or molecule can be distorted or displaced from their normal positions in response to an applied electric field. It is a fundamental property that determines the strength of interactions between charged particles and neutral atoms or molecules.
Potential Energy: Potential energy is the stored energy in an object due to its position or configuration in a force field, such as gravitational or electric fields. This form of energy can be converted into kinetic energy when the object is allowed to move or change position, playing a crucial role in various physical systems. Understanding potential energy helps explain how electric forces act between charges and the concept of voltage in electric circuits.
Torque: Torque is a measure of the rotational force that causes an object to rotate about an axis, fulcrum, or pivot. It is the product of the force applied and the distance between the line of action of the force and the axis of rotation.
Uniform Electric Field: A uniform electric field is a region of space where the electric field is constant in both magnitude and direction. This means the electric field lines are parallel and evenly spaced, creating a uniform force on any charged particles within the field.
Water (H2O): Water is a colorless, odorless, and tasteless liquid that is essential for life. It is the most abundant compound on Earth's surface and is composed of two hydrogen atoms and one oxygen atom. Water plays a crucial role in various physical and chemical processes, making it a fundamental substance for the functioning of living organisms and the environment.
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