Physics · MU Sofia

14. Electric field

Introduces electric field intensity, defined as force per unit test charge, and the potential of a point charge, with Coulomb's constant. It then covers the electric dipole in vacuum and how material media alter fields through orientational and induced polarization. The note closes with capacitor capacity and the dielectric constant's effect on stored energy and field strength.

Inside: 1 section · 9 labelled pictures · 11 flashcards · 3 min

Topic 15 of 42 in the MU Sofia syllabus for Physics (Dental Medicine, Year 1). The free AceMed note covers it in 1 section, about 451 words (3 min of reading), with 11 flashcards.

In this note

  1. Introduction

Introduction

Summary

  • The study of electric fields includes understanding intensity and potential, especially concerning point charges and electric dipoles in a vacuum. Electric dipoles consist of two point charges of equal magnitude but opposite signs, separated by a distance, generating a specific field pattern. In material mediums, electric fields are influenced by the medium's properties, leading to orientational and induced polarization, affecting the electric potential energy and movement of charges. The concepts of dielectric constant and electric capacity are integral to understanding how materials influence electric fields and their ability to store electrical energy, particularly in configurations like capacitors with oppositely charged plates.
  • Electric Field Intensity and Potential:
  • Electric field intensity (E) describes the force per unit charge exerted on a test charge in the field, calculated as (E = F/q).
  • Potential of Point Charge: The electric potential (V) due to a point charge (Q) at a distance (r) is given by V=krQ​, where k is Coulomb's constant. This formula underscores the influence of a charge's magnitude and distance on the electric potential in its vicinity.
  • Electric Dipole in Vacuum:
  • An electric dipole consists of two point charges of equal strength but opposite signs, separated by a fixed distance (p = q\p.d), affecting the surrounding electric field pattern.
  • Electric Field in Material Medium:
  • The presence of electric charges causes an electric field in the surrounding environment, with field lines indicating the direction and magnitude of the force.
  • Material mediums modify the electric field through orientational and induced polarization.
  • Orientational and Induced Polarization:
  • Orientational Polarization: Occurs when permanent dipoles within a material align with an external electric field.
  • Induced Polarization: Results from the deformation of the electron cloud in atoms or molecules, creating temporary dipoles in response to an external field.
  • These processes lead to a redistribution of charges, affecting the material's overall electric properties.
  • Orientated and Induced polarization formula :
  • Electric Capacity of a Conductor:
  • A conductor's electric capacity relates to its ability to store electric charge, exemplified by a capacitor consisting of two plates (one negatively and one positively charged) of the same magnitude.
  • The charge on the conductor remains constant, but its ability to store charge is influenced by the separation distance between the plates and the presence of a dielectric material, which can increase the system's overall capacity.
  • Dielectric Constant :

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