Electric charge

Electric field of a positive and a negative point charge
Diagram showing field lines and equipotentials around an electron, a negatively charged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons (which are positively charged), resulting in a net zero overall charge
Coulomb's torsion balance

Physical property of matter that causes it to experience a force when placed in an electromagnetic field.

- Electric charge

500 related topics


Ampere hour

Rechargeable batteries Top: AA battery (2500 mA⋅h) Bottom: AAA battery (1000 mA⋅h)

An ampere hour or amp hour (symbol: A⋅h or A h; often also unofficially denoted as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3,600 coulombs.


Charles-Augustin de Coulomb, the unit's namesake

The coulomb (symbol: C) is the SI derived unit of electric charge.


Smallest unit of ordinary matter that forms a chemical element.

Atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy vol. 1 (1808)
The Geiger–Marsden experiment:
Left: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.
Right: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus.
The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete.
The binding energy needed for a nucleon to escape the nucleus, for various isotopes
A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
This diagram shows the half-life (T½) of various isotopes with Z protons and N neutrons.
These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. Do not forget that even the top of the diagram is lower than an unbound electron state.
An example of absorption lines in a spectrum
Graphic illustrating the formation of a Bose–Einstein condensate
Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them (See surface reconstruction).
Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process.

The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge.


Type of elementary particle and a fundamental constituent of matter.

A proton is composed of two up quarks, one down quark, and the gluons that mediate the forces "binding" them together. The color assignment of individual quarks is arbitrary, but all three colors must be present; red, blue and green are used as an analogy to the primary colors that together produce a white color.
Six of the particles in the Standard Model are quarks (shown in purple). Each of the first three columns forms a generation of matter.
Murray Gell-Mann (2007)
George Zweig (2015)
Photograph of the event that led to the discovery of the baryon, at the Brookhaven National Laboratory in 1974
Feynman diagram of beta decay with time flowing upwards. The CKM matrix (discussed below) encodes the probability of this and other quark decays.
The strengths of the weak interactions between the six quarks. The "intensities" of the lines are determined by the elements of the CKM matrix.
All types of hadrons have zero total color charge.
The pattern of strong charges for the three colors of quark, three antiquarks, and eight gluons (with two of zero charge overlapping).
Current quark masses for all six flavors in comparison, as balls of proportional volumes. Proton (gray) and electron (red) are shown in bottom left corner for scale.
A qualitative rendering of the phase diagram of quark matter. The precise details of the diagram are the subject of ongoing research.

Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin.

Electric field

Physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them.

Effects of an electric field. The girl is touching an electrostatic generator, which charges her body with a high voltage. Her hair, which is charged with the same polarity, is repelled by the electric field of her head and stands out from her head.
Electric field of a positive point electric charge suspended over an infinite sheet of conducting material. The field is depicted by electric field lines, lines which follow the direction of the electric field in space.
Evidence of an electric field: styrofoam peanuts clinging to a cat's fur due to static electricity. The triboelectric effect causes an electrostatic charge to build up on the fur due to the cat's motions. The electric field of the charge causes polarization of the molecules of the styrofoam due to electrostatic induction, resulting in a slight attraction of the light plastic pieces to the charged fur. This effect is also the cause of static cling in clothes.
Illustration of the electric field surrounding a positive (red) and a negative (blue) charge
Illustration of the electric field between two parallel conductive plates of finite size (known as a parallel plate capacitor). In the middle of the plates, far from any edges, the electric field is very nearly uniform.
The electric field (lines with arrows) of a charge (+) induces surface charges ( red and blue areas) on metal objects due to electrostatic induction.

The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test charge at rest at that point.

Quantum electrodynamics

Relativistic quantum field theory of electrodynamics.

Paul Dirac
Hans Bethe
Feynman (center) and Oppenheimer (right) at Los Alamos.
Feynman diagram elements
Compton scattering
Feynman replaces complex numbers with spinning arrows, which start at emission and end at detection of a particle. The sum of all resulting arrows gives a final arrow whose length squared equals the probability of the event. In this diagram, light emitted by the source S can reach the detector at P by bouncing off the mirror (in blue) at various points. Each one of the paths has an arrow associated with it (whose direction changes uniformly with the time taken for the light to traverse the path). To correctly calculate the total probability for light to reach P starting at S, one needs to sum the arrows for all such paths. The graph below depicts the total time spent to traverse each of the paths above.
Addition of probability amplitudes as complex numbers
Multiplication of probability amplitudes as complex numbers
Electron self-energy loop
One-loop contribution to the vacuum polarization function <math>\Pi</math>
One-loop contribution to the electron self-energy function <math>\Sigma</math>
One-loop contribution to the vertex function <math>\Gamma</math>
Multiplication of probability amplitudes as complex numbers

QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction.


An electrostatic effect: foam peanuts clinging to a cat's fur due to static electricity. The triboelectric effect causes an electrostatic charge to build up on the surface of the fur due to the cat's motions. The electric field of the charge causes polarization of the molecules of the foam due to electrostatic induction, resulting in a slight attraction of the light plastic pieces to the charged fur.   This effect is also the cause of static cling in clothes.
The electrostatic field (lines with arrows) of a nearby positive charge (+)  causes the mobile charges in conductive objects to separate due to electrostatic induction. Negative charges  (blue)  are attracted and move to the surface of the object facing the external charge. Positive charges  (red)  are repelled and move to the surface facing away. These induced surface charges are exactly the right size and shape so their opposing electric field cancels the electric field of the external charge throughout the interior of the metal. Therefore, the electrostatic field everywhere inside a conductive object is zero, and the electrostatic potential is constant.
Lightning over Oradea in Romania

Electrostatics is a branch of physics that studies electric charges at rest (static electricity).

Physical property

Any property that is measurable, whose value describes a state of a physical system.

Property dualism: the exemplification of two kinds of property by one kind of substance

electric charge

Charged particle

Various examples of physical phenomena

In physics, a charged particle is a particle with an electric charge.

Electromagnetic field

A sinusoidal electromagnetic wave propagating along the positive z-axis, showing the electric field (blue) and magnetic field (red) vectors.

An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by accelerating electric charges.