Electrostatics Fundamentals: Charge, Conductors, and Coulomb’s Law

Posted on Aug 12, 2025 in Chemistry

Electrostatics: The Study of Static Electric Charges

Electrostatics is the study of electric charges at rest. Objects can be electrified through three primary methods:

  • Friction
  • Contact
  • Induction

Electric Charges (Q) and Atomic Structure

  • Protons and electrons possess electric charges (positive and negative, respectively).
  • Forces of attraction between these particles form atoms.
  • Every atom consists of a positively charged nucleus surrounded by negatively charged electrons.
  • Electrons across all atoms are identical, each possessing the same electric charge and mass.
  • Protons and neutrons constitute the atom’s nucleus. Protons and electrons carry the same magnitude of charge.
  • Generally, atoms are electrically neutral, possessing an equal number of protons and electrons. Otherwise, they are called ions.
  • Protons within the nucleus do not repel due to nuclear forces being stronger than the electrical repulsion, binding them together.
  • Electrons orbit the nucleus and do not collapse into it due to the wave nature of the atom.
  • The SI unit for electric charge is the coulomb (C), equivalent to the charge of approximately 6.25 x 1018 electrons.

Properties of Electric Charge

  • Electric charges exhibit a property called charge conservation, which states that charge is neither created nor destroyed, but merely transferred from one object to another, for example, through rubbing.
  • Another property, known as the quantization of electric charge, indicates that when an object becomes electrically charged, its total charge will be an integer multiple of the fundamental charge (the magnitude of the charge of an electron or proton, approximately 1.6 x 10-19 C).

Conductors, Insulators, and Semiconductors

  • Conductors are materials possessing many free electrons that are not tightly bound to their atomic nuclei.
  • Insulators (or dielectric materials) are those in which electrons are tightly bound to the nucleus, preventing or hindering the passage of electric charge. They are also generally poor conductors of heat.
  • All substances can be classified based on their ability to conduct electrical charges.
  • Additionally, there are semiconductors and superconductors. Semiconductors act as conductors at certain temperatures and as insulators at others. Superconductors exhibit zero electrical resistance, allowing for perfect conductivity.

Methods of Electrification

Electrification by Friction

Occurs when two neutral bodies or substances become charged due to the transfer of electrons through rubbing. The bodies acquire opposite charges.

Electrification by Contact

Occurs when a charged body touches a neutral body. In this process, the charged body transfers electrons to the neutral body, but not enough to become neutral itself. Both bodies end up with the same type of charge.

Electrification by Induction

Occurs when a charged object is brought near two neutral objects that are in contact. The presence of the charged object causes a rearrangement of charges within the neutral objects, resulting in one becoming positively charged and the other negatively charged, without direct contact.

Coulomb’s Law: Quantifying Electric Force

The magnitude of a body’s charge can be theoretically determined by the number of electrons it gains or loses. However, expressing charge this way is impractical because electrification processes involve the transfer of a vast number of electrons, leading to extremely large numerical values. Therefore, in practice, a more convenient unit, the coulomb, is used.