Electric Charge

  • Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge: positive and negative. Like charges repel and unlike attract. An object with an absence of net charge is referred to as neutral.
  • Electric charge measures how strongly an object experiences electrical forces
  • Electric charge is measured in Coulombs

Neutral Hydrogen

  • Neutral hydrogen is a normal, electrically neutral hydrogen atom with one proton and one electron. It is commonly referred to as HI (pronounced H-one), and is located throughout galaxies as HI clouds or external to galaxies as part of the intercloud gas.

Hydrogen Line

  • The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.

Coulomb’s Law

  • Coulomb’s law, or Coulomb’s inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationaries, electrically charged particles. The electric force between charged bodies at rest is conventionally called electrostatic force or Coulomb force.


  • A conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors.
  • Charge can move freely
  • Earth acts as an “infinite sink or source”
  • After the connection is broken, the charges are stuck on the object even the external charge is removed


  • An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily.
  • Charges cannot move freely but they can polarize

Electric Fields

  • An electric field surrounds an electric charge, and exerts force on other charges in the field, attracting or repelling them. Electric field is sometimes abbreviated as E-field.

Electric Potential

  • An electric potential is the amount of work needed to move a unit of charge from a reference point to a specific point inside the field without producing an acceleration.

Electric Potential Energy

  • Electric potential energy, or Static potential energy, is a potential energy that results from conservative Coulomb forces and is associated with the configuration of a particular set of point charges within a defined system.


  • Voltage is the difference in potential between two arbitrary points at which the potential is not necessarily zero.


  • Electricity is also a conservative force


  • Electrostatics is a branch of physics that studies electric charges at rest. Since classical physics, it has been known that some materials, such as amber, attract lightweight particles after rubbing.