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is a fundamental interaction between . It's the invisible push or pull that makes opposites attract and likes repel. This force follows Coulomb's Law, which tells us how strong it is based on charge size and distance.

Understanding is key to grasping electromagnetism. It explains everything from static cling to lightning strikes. By learning Coulomb's Law, you'll be able to calculate and predict how charged objects interact in various situations.

Electric Force and Coulomb's Law

Electric force and charged particles

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  • Electric force fundamental force acts between electrically charged particles
    • Charged particles can be positively () or negatively () charged
    • Like charges repel each other (two positive charges push away), while opposite charges attract each other (positive and negative charges pull together)
  • Strength of electric force depends on magnitude of charges and distance between them
    • Larger charges result in stronger electric force (doubling charge quadruples force)
    • Force decreases as distance between charges increases (doubling distance reduces force to one-fourth)

Coulomb's Law calculations

  • Coulomb's Law describes magnitude of electric force between two
    • Formula for Coulomb's Law: [F](https://www.fiveableKeyTerm:F)=[k](https://www.fiveableKeyTerm:k)∣q1∣∣q2∣[r](https://www.fiveableKeyTerm:r)2[F](https://www.fiveableKeyTerm:F) = [k](https://www.fiveableKeyTerm:k) \frac{|q_1||q_2|}{[r](https://www.fiveableKeyTerm:r)^2}
      • FF magnitude of electric force ()
      • kk , approximately 8.99×109N⋅m2C28.99 \times 10^9 \frac{N \cdot m^2}{C^2}
      • ∣q1∣|q_1| and ∣q2∣|q_2| absolute values of charges ()
      • rr distance between two charges (meters)
  • To calculate electric force, substitute given values into formula and solve for FF
    • Ensure units are consistent (charges in Coulombs, distance in meters)
    • Example: Two charges of +2 and -3 µC separated by 5 cm
      1. Convert units (µC to C, cm to m)
      2. Substitute values: F=(8.99×109)(2×10−6)(3×10−6)(0.05)2F = (8.99 \times 10^9) \frac{(2 \times 10^{-6})(3 \times 10^{-6})}{(0.05)^2}
      3. Calculate: F=2.16×10−3NF = 2.16 \times 10^{-3} N
  • Coulomb's Law follows the , where the force is inversely proportional to the square of the distance between charges

Direction of electric forces

  • Direction of electric force depends on signs of charges involved
    • If both charges have same sign (both positive or both negative), force is repulsive
      • Charges experience force pushing them away from each other (like ends of two magnets)
    • If charges have opposite signs (one positive, one negative), force is attractive
      • Charges experience force pulling them towards each other (opposite ends of two magnets)
  • To determine direction of force, consider signs of charges and relative positions
    • Positive charge will be pushed away from another positive charge
    • Negative charge will be pulled towards a positive charge
    • Direction always along line connecting centers of charges

Superposition principle for multiple charges

  • states total electric force on charge is of individual forces exerted by all other charges
    • To find net force on charge, calculate force due to each individual charge and add as vectors
      • Vector addition takes into account both magnitude and direction of forces
      • Net force on charge can be zero if individual forces cancel each other out (forces in opposite directions)
  • When applying superposition principle, calculate force between each pair of charges separately
    • Determine magnitude of each force using Coulomb's Law
    • Determine direction of each force based on signs of charges (repulsive or attractive)
  • Add individual forces as vectors to find net force on charge of interest
    • Break vectors into components (x and y directions)
    • Add components separately, then find resultant vector
    • Example: Three charges arranged in a line, +2 µC at origin, -4 µC at (3,0), +1 µC at (0,4)
      1. Calculate forces on +2 µC charge due to other two charges
      2. Find x and y components of each force
      3. Add x components, add y components
      4. Find magnitude and direction of resultant force vector

Electric Fields and Permittivity

  • Electric field is a region around a charged particle where it exerts an on other charged particles
  • is a measure of how easily an electric field can be established in a medium
    • (ε₀) is the permittivity of free space, a fundamental constant in electromagnetism
  • The strength of the electric field and the are influenced by the permittivity of the medium

Key Terms to Review (25)

Attractive Force: An attractive force is a type of force that draws objects together. It is a fundamental interaction in nature that causes objects with opposite charges or masses to be pulled towards each other, resulting in a net attractive force between them.
Charged particles: Charged particles are entities that carry an electric charge, either positive or negative, which results from an imbalance of electrons and protons. They are fundamental components of matter and play a critical role in the interactions described by Coulomb's Law, which quantifies the force between two charged objects based on their charges and the distance between them. Understanding charged particles is essential for grasping how electric forces operate in various physical systems.
Coulomb's Constant: Coulomb's constant, also known as the electrostatic constant or the electric force constant, is a fundamental physical constant that describes the strength of the electrostatic force between two point charges. It is a crucial parameter in understanding and quantifying various electrical phenomena, including Coulomb's law, electric fields, electric flux, electric potential energy, and applications of electrostatics.
Coulombs: Coulombs is the unit of electric charge in the International System of Units (SI). It is named after the French physicist Charles-Augustin de Coulomb, who pioneered the study of electrostatic forces and their relationship to electric charge. Coulombs are used to quantify the amount of electric charge in various contexts, particularly in the study of Coulomb's Law.
Electric force: Electric force is the attractive or repulsive interaction between any two charged objects. It is governed by Coulomb's Law, which states that the magnitude of the force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
Electric Force: Electric force is the force of attraction or repulsion between charged particles. It is the fundamental force that governs the behavior of charged objects and is described by Coulomb's law. This force is responsible for the creation of electric fields and the potential energy stored in those fields.
Electrons: Electrons are subatomic particles that carry a negative electric charge and are found in all atoms. They play a crucial role in various physical phenomena, including Coulomb's law, electrical current, the motion of charged particles in magnetic fields, and the Hall effect.
Electrostatic force: Electrostatic force is the force of attraction or repulsion between two charged objects. It is described by Coulomb's law and acts along the line joining the centers of two charges.
Electrostatic Force: Electrostatic force is the force of attraction or repulsion between stationary electric charges. It is a fundamental force in nature that governs the behavior of charged particles and plays a crucial role in various electrical and electronic phenomena.
F: F is a symbol that represents the force between two charged particles, as described by Coulomb's Law. This force is a fundamental concept in electrostatics and is crucial for understanding the behavior of charged objects and the interactions between them.
Free electrons: Free electrons are electrons that are not bound to atoms and can move freely within a material. In conductors, these free electrons enable the flow of electric current.
Inverse Square Law: The inverse square law is a fundamental principle that describes how the strength or intensity of a force or field decreases with the distance from the source. It states that the strength or intensity of a force or field is inversely proportional to the square of the distance from the source.
K: k is a fundamental constant in physics that represents the proportionality factor in Coulomb's law, which describes the electrostatic force between two charged particles. It is a dimensionless quantity that is essential in understanding the behavior of electric charges and the interactions between them.
Newtons: Newtons are the units used to measure force, which is the interaction that can cause an object to change its velocity, shape, or direction. Newtons are a fundamental unit in the study of physics and are particularly relevant in the context of Coulomb's Law, which describes the force between electric charges.
Permittivity: Permittivity is a physical constant that describes how an electric field affects, and is affected by, a dielectric medium. It plays a crucial role in determining the strength and behavior of electric fields, influencing both the force between charges and the energy stored in capacitors. The value of permittivity varies depending on the material, affecting how electric fields interact with matter and is central to understanding capacitors and electromagnetic waves.
Permittivity of vacuum: The permittivity of vacuum, denoted as $\varepsilon_0$, is a physical constant that characterizes the ability of the vacuum to permit electric field lines. It is essential in calculating the force between two charges in a vacuum using Coulomb's Law.
Point Charges: A point charge is an idealized model of an electric charge that is considered to have no physical size or dimension. It is a mathematical abstraction used to simplify the analysis of electric fields and the interactions between charged particles.
Principle of superposition: The principle of superposition states that the net electric field caused by multiple charges is the vector sum of the electric fields produced by each charge individually. It allows for the calculation of complex electric fields by breaking them down into simpler components.
Protons: Protons are positively charged subatomic particles found in the nucleus of an atom. They play a crucial role in determining the atomic number of an element, which defines its identity and chemical properties. Protons, along with neutrons, make up the mass of an atom and interact with electrons to form the basis of chemical bonding.
R: The variable 'r' is a fundamental quantity that represents the distance between two points or objects in space. It is a vector quantity, meaning it has both magnitude and direction, and is commonly used in physics to describe the spatial relationship between interacting entities.
Repulsive force: A repulsive force is a type of force that pushes two objects away from each other, often occurring between like charges in electrostatics. This force arises from the interaction of electric charges, where two objects with the same charge (either positive or negative) experience a push apart. Understanding this concept is crucial for grasping the behavior of charged particles and the fundamental principles governing electric forces.
Superposition Principle: The superposition principle states that the net effect of multiple sources or influences acting on a system is the sum of their individual effects. This principle is fundamental in understanding various physical phenomena, particularly in the fields of electricity, magnetism, and wave mechanics.
Vacuum Permittivity: Vacuum permittivity, also known as the permittivity of free space, is a fundamental physical constant that describes the ability of a vacuum to support an electric field. It is a measure of the electrical properties of a vacuum and is a key parameter in Coulomb's law, which governs the force between two electric charges.
Vector Sum: The vector sum, also known as the resultant vector, is the combined effect of two or more vectors acting on an object. It represents the single vector that has the same overall effect as the individual vectors combined.
µC: The micro-Coulomb (µC) is a unit of electric charge in the International System of Units (SI). It is a submultiple of the Coulomb, the SI unit of electric charge, with 1 Coulomb being equal to 1,000,000 micro-Coulombs (1 C = 1,000,000 µC).
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Glossary
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5.4 Electric Field