Charge Definition and Examples (Physics and Chemistry)

Learn What Charge Means in Science

In physics and chemistry, the term "charge" refers to electrical charge.
In physics and chemistry, the term "charge" refers to electrical charge. SCIENCE PHOTO LIBRARY / Getty Images

In the context of chemistry and physics, charge usually refers to electric charge, which is a conserved property of certain subatomic particles that determines their electromagnetic interaction. Charge is a physical property that causes matter to experience a force within an electromagnetic field. Electric charges may be positive or negative in nature. If no net electric charge is present, the matter is considered to be neutral or uncharged. Like charges (e.g., two positive charges or two negative charges) repel each other. Dissimilar charges (positive and negative) attract each other.

In physics, the term "charge" may also refer to color charge in the field of quantum chromodynamics. In general, charge refers to a generator of continuous symmetry in a system.

Charge Examples in Science

  • By convention, electrons have a charge of -1 while protons have a charge of +1. Another way of indicating charge is for an electron to have a charge of e and a proton to have a charge of +e.
  • Quarks possess what is known as color charge.
  • Quarks may possess flavor charges, including charm and strangeness.
  • Although hypothetical, magnetic charge has been postulated for electromagnetism.

Units of Electric Charge

The proper unit for electric charge is discipline-dependent. In chemistry, a capital letter Q is used to indicate charge in equations, with the elementary charge of an electron (e) as a common unit. The SI derived unit of charge is the coulomb (C). Electrical engineering often uses the unit ampere-hour (Ah) for charge.