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96-473: The coulomb (symbol: C ) is the unit of electric charge in the International System of Units (SI). It is equal to the electric charge delivered by a 1 ampere current in 1 second and is defined in terms of the elementary charge e , at about 6.241 509 × 10  e . The SI defines the coulomb by taking the value of the elementary charge e to be 1.602 176 634 × 10 C , but

192-490: A ballistic galvanometer . The elementary charge (the electric charge of the proton) is defined as a fundamental constant in the SI. The value for elementary charge, when expressed in SI units, is exactly 1.602 176 634 × 10  C . After discovering the quantized character of charge, in 1891, George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. J. J. Thomson subsequently discovered

288-402: A deuteron [NP], and also between protons and protons, and neutrons and neutrons. The effective absolute limit of the range of the nuclear force (also known as residual strong force ) is represented by halo nuclei such as lithium-11 or boron-14 , in which dineutrons , or other collections of neutrons, orbit at distances of about 10 fm (roughly similar to the 8 fm radius of

384-585: A characteristic property of many subatomic particles . The charges of free-standing particles are integer multiples of the elementary charge e ; we say that electric charge is quantized . Michael Faraday , in his electrolysis experiments, was the first to note the discrete nature of electric charge. Robert Millikan 's oil drop experiment demonstrated this fact directly, and measured the elementary charge. It has been discovered that one type of particle, quarks , have fractional charges of either − ⁠ 1 / 3 ⁠ or + ⁠ 2 / 3 ⁠ , but it

480-445: A continuous quantity, even at the microscopic level. Static electricity refers to the electric charge of an object and the related electrostatic discharge when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects. When a piece of glass and a piece of resin—neither of which exhibit any electrical properties—are rubbed together and left with

576-448: A diminutive of nux ('nut'), meaning 'the kernel' (i.e., the 'small nut') inside a watery type of fruit (like a peach ). In 1844, Michael Faraday used the term to refer to the "central point of an atom". The modern atomic meaning was proposed by Ernest Rutherford in 1912. The adoption of the term "nucleus" to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article The Atom and

672-418: A flow of electrons; a flow of electron holes that act like positive particles; and both negative and positive particles ( ions or other charged particles) flowing in opposite directions in an electrolytic solution or a plasma . Beware that, in the common and important case of metallic wires, the direction of the conventional current is opposite to the drift velocity of the actual charge carriers; i.e.,

768-462: A flow of this fluid constitutes an electric current. He also posited that when matter contained an excess of the fluid it was positively charged and when it had a deficit it was negatively charged. He identified the term positive with vitreous electricity and negative with resinous electricity after performing an experiment with a glass tube he had received from his overseas colleague Peter Collinson. The experiment had participant A charge

864-470: A limited range because it decays quickly with distance (see Yukawa potential ); thus only nuclei smaller than a certain size can be completely stable. The largest known completely stable nucleus (i.e. stable to alpha, beta , and gamma decay ) is lead-208 which contains a total of 208 nucleons (126 neutrons and 82 protons). Nuclei larger than this maximum are unstable and tend to be increasingly short-lived with larger numbers of nucleons. However, bismuth-209

960-404: A magnetic field) is the source of the electromagnetic (or Lorentz) force , which is one of the four fundamental interactions in physics . The study of photon -mediated interactions among charged particles is called quantum electrodynamics . The SI derived unit of electric charge is the coulomb (C) named after French physicist Charles-Augustin de Coulomb . In electrical engineering it

1056-428: A net charge of zero, thus making the atom neutral. An ion is an atom (or group of atoms) that has lost one or more electrons, giving it a net positive charge (cation), or that has gained one or more electrons, giving it a net negative charge (anion). Monatomic ions are formed from single atoms, while polyatomic ions are formed from two or more atoms that have been bonded together, in each case yielding an ion with

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1152-404: A positive or negative net charge. During the formation of macroscopic objects, constituent atoms and ions usually combine to form structures composed of neutral ionic compounds electrically bound to neutral atoms. Thus macroscopic objects tend toward being neutral overall, but macroscopic objects are rarely perfectly net neutral. Sometimes macroscopic objects contain ions distributed throughout

1248-491: A positively charged core of radius ≈ 0.3 fm surrounded by a compensating negative charge of radius between 0.3 fm and 2 fm. The proton has an approximately exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm. The shape of the atomic nucleus can be spherical, rugby ball-shaped (prolate deformation), discus-shaped (oblate deformation), triaxial (a combination of oblate and prolate deformation) or pear-shaped. Nuclei are bound together by

1344-448: A proton + neutron (the deuteron) can exhibit bosonic behavior when they become loosely bound in pairs, which have integer spin. In the rare case of a hypernucleus , a third baryon called a hyperon , containing one or more strange quarks and/or other unusual quark(s), can also share the wave function. However, this type of nucleus is extremely unstable and not found on Earth except in high-energy physics experiments. The neutron has

1440-468: A rubbed glass received the same, but opposite, charge strength as the cloth used to rub the glass. Franklin imagined electricity as being a type of invisible fluid present in all matter and coined the term charge itself (as well as battery and some others ); for example, he believed that it was the glass in a Leyden jar that held the accumulated charge. He posited that rubbing insulating surfaces together caused this fluid to change location, and that

1536-432: A significant degree, either positively or negatively. Charge taken from one material is moved to the other material, leaving an opposite charge of the same magnitude behind. The law of conservation of charge always applies, giving the object from which a negative charge is taken a positive charge of the same magnitude, and vice versa. Even when an object's net charge is zero, the charge can be distributed non-uniformly in

1632-444: A single neutron halo include Be and C. A two-neutron halo is exhibited by He, Li, B, B and C. Two-neutron halo nuclei break into three fragments, never two, and are called Borromean nuclei because of this behavior (referring to a system of three interlocked rings in which breaking any ring frees both of the others). He and Be both exhibit a four-neutron halo. Nuclei which have a proton halo include B and P. A two-proton halo

1728-411: A soul. In other words, there was no indication of any conception of electric charge. More generally, the ancient Greeks did not understand the connections among these four kinds of phenomena. The Greeks observed that the charged amber buttons could attract light objects such as hair . They also found that if they rubbed the amber for long enough, they could even get an electric spark to jump, but there

1824-431: A sphere of positive charge. Ernest Rutherford later devised an experiment with his research partner Hans Geiger and with help of Ernest Marsden , that involved the deflection of alpha particles (helium nuclei) directed at a thin sheet of metal foil. He reasoned that if J. J. Thomson's model were correct, the positively charged alpha particles would easily pass through the foil with very little deviation in their paths, as

1920-440: A thread, it was possible to make the lead become electrified (e.g., to attract and repel brass filings). He attempted to explain this phenomenon with the idea of electrical effluvia. Gray's discoveries introduced an important shift in the historical development of knowledge about electric charge. The fact that electrical effluvia could be transferred from one object to another, opened the theoretical possibility that this property

2016-416: A two-fluid theory. When glass was rubbed with silk , du Fay said that the glass was charged with vitreous electricity , and, when amber was rubbed with fur, the amber was charged with resinous electricity . In contemporary understanding, positive charge is now defined as the charge of a glass rod after being rubbed with a silk cloth, but it is arbitrary which type of charge is called positive and which

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2112-476: A variety of known forms, which he characterized as common electricity (e.g., static electricity , piezoelectricity , magnetic induction ), voltaic electricity (e.g., electric current from a voltaic pile ), and animal electricity (e.g., bioelectricity ). In 1838, Faraday raised a question about whether electricity was a fluid or fluids or a property of matter, like gravity. He investigated whether matter could be charged with one kind of charge independently of

2208-582: Is also a claim that no mention of electric sparks appeared until late 17th century. This property derives from the triboelectric effect . In late 1100s, the substance jet , a compacted form of coal, was noted to have an amber effect, and in the middle of the 1500s, Girolamo Fracastoro , discovered that diamond also showed this effect. Some efforts were made by Fracastoro and others, especially Gerolamo Cardano to develop explanations for this phenomenon. In contrast to astronomy , mechanics , and optics , which had been studied quantitatively since antiquity,

2304-454: Is also common to use the ampere-hour (A⋅h). In physics and chemistry it is common to use the elementary charge ( e ) as a unit. Chemistry also uses the Faraday constant , which is the charge of one mole of elementary charges. Charge is the fundamental property of matter that exhibits electrostatic attraction or repulsion in the presence of other matter with charge. Electric charge is

2400-415: Is also stable to beta decay and has the longest half-life to alpha decay of any known isotope, estimated at a billion times longer than the age of the universe. The residual strong force is effective over a very short range (usually only a few femtometres (fm); roughly one or two nucleon diameters) and causes an attraction between any pair of nucleons. For example, between a proton and a neutron to form

2496-481: Is approximately 6 241 509 074 460 762 607 .776  e (and is thus not an integer multiple of the elementary charge), where the number is the reciprocal of 1.602 176 634 × 10 C . The coulomb is exactly 1   C = 1 1.602 176 634 × 10 − 19   e . {\displaystyle 1~\mathrm {C} ={\frac {1}{1.602\,176\,634\times 10^{-19}}}~e.} Like other SI units,

2592-440: Is believed they always occur in multiples of integral charge; free-standing quarks have never been observed. By convention , the charge of an electron is negative, −e , while that of a proton is positive, +e . Charged particles whose charges have the same sign repel one another, and particles whose charges have different signs attract. Coulomb's law quantifies the electrostatic force between two particles by asserting that

2688-487: Is called negative. Another important two-fluid theory from this time was proposed by Jean-Antoine Nollet (1745). Up until about 1745, the main explanation for electrical attraction and repulsion was the idea that electrified bodies gave off an effluvium. Benjamin Franklin started electrical experiments in late 1746, and by 1750 had developed a one- fluid theory of electricity , based on an experiment that showed that

2784-448: Is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms . If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized : it comes in integer multiples of individual small units called the elementary charge , e , about 1.602 × 10  C , which

2880-410: Is credited with coining the terms conductors and insulators to refer to the effects of different materials in these experiments. Gray also discovered electrical induction (i.e., where charge could be transmitted from one object to another without any direct physical contact). For example, he showed that by bringing a charged glass tube close to, but not touching, a lump of lead that was sustained by

2976-468: Is defined as the charge carried by an electron and a positive charge is that carried by a proton . Before these particles were discovered, a positive charge was defined by Benjamin Franklin as the charge acquired by a glass rod when it is rubbed with a silk cloth. Electric charges produce electric fields . A moving charge also produces a magnetic field . The interaction of electric charges with an electromagnetic field (a combination of an electric and

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3072-409: Is due to two reasons: Historically, experiments have been compared to relatively crude models that are necessarily imperfect. None of these models can completely explain experimental data on nuclear structure. The nuclear radius ( R ) is considered to be one of the basic quantities that any model must predict. For stable nuclei (not halo nuclei or other unstable distorted nuclei) the nuclear radius

3168-423: Is exhibited by Ne and S. Proton halos are expected to be more rare and unstable than the neutron examples, because of the repulsive electromagnetic forces of the halo proton(s). Although the standard model of physics is widely believed to completely describe the composition and behavior of the nucleus, generating predictions from theory is much more difficult than for most other areas of particle physics . This

3264-425: Is much more complex than simple closure of shell orbitals with magic numbers of protons and neutrons. For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to

3360-474: Is obtained by integrating both sides: where I is the net outward current through a closed surface and q is the electric charge contained within the volume defined by the surface. Aside from the properties described in articles about electromagnetism , charge is a relativistic invariant . This means that any particle that has charge q has the same charge regardless of how fast it is travelling. This property has been experimentally verified by showing that

3456-745: Is otherwise in lower case. By 1878, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb. In 1881, the International Electrical Congress , now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force, the ampere as the unit for electric current, and the coulomb as the unit of electric charge. At that time,

3552-445: Is preceded and followed by 17 or more stable elements. There are however problems with the shell model when an attempt is made to account for nuclear properties well away from closed shells. This has led to complex post hoc distortions of the shape of the potential well to fit experimental data, but the question remains whether these mathematical manipulations actually correspond to the spatial deformations in real nuclei. Problems with

3648-534: Is proportional to the volume. Surface energy . A nucleon at the surface of a nucleus interacts with fewer other nucleons than one in the interior of the nucleus and hence its binding energy is less. This surface energy term takes that into account and is therefore negative and is proportional to the surface area. Coulomb energy . The electric repulsion between each pair of protons in a nucleus contributes toward decreasing its binding energy. Asymmetry energy (also called Pauli Energy). An energy associated with

3744-518: Is roughly proportional to the cube root of the mass number ( A ) of the nucleus, and particularly in nuclei containing many nucleons, as they arrange in more spherical configurations: The stable nucleus has approximately a constant density and therefore the nuclear radius R can be approximated by the following formula, where A = Atomic mass number (the number of protons Z , plus the number of neutrons N ) and r 0  = 1.25 fm = 1.25 × 10  m. In this equation,

3840-433: Is said to be resinously electrified. All electrified bodies are either vitreously or resinously electrified. An established convention in the scientific community defines vitreous electrification as positive, and resinous electrification as negative. The exactly opposite properties of the two kinds of electrification justify our indicating them by opposite signs, but the application of the positive sign to one rather than to

3936-447: Is successful at explaining many important phenomena of nuclei, such as their changing amounts of binding energy as their size and composition changes (see semi-empirical mass formula ), but it does not explain the special stability which occurs when nuclei have special "magic numbers" of protons or neutrons. The terms in the semi-empirical mass formula, which can be used to approximate the binding energy of many nuclei, are considered as

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4032-462: Is that sharing of electrons to create stable electronic orbits about the nuclei that appears to us as the chemistry of our macro world. Protons define the entire charge of a nucleus, and hence its chemical identity . Neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons can explain the phenomenon of isotopes (same atomic number with different atomic mass). The main role of neutrons

4128-431: Is the coulomb (symbol: C). The coulomb is defined as the quantity of charge that passes through the cross section of an electrical conductor carrying one ampere for one second . This unit was proposed in 1946 and ratified in 1948. The lowercase symbol q is often used to denote a quantity of electric charge. The quantity of electric charge can be directly measured with an electrometer , or indirectly measured with

4224-477: Is the smallest charge that can exist freely. Particles called quarks have smaller charges, multiples of ⁠ 1 / 3 ⁠ e , but they are found only combined in particles that have a charge that is an integer multiple of e . In the Standard Model , charge is an absolutely conserved quantum number. The proton has a charge of + e , and the electron has a charge of − e . Today, a negative charge

4320-483: Is to be nonpolarized, and that when polarized, they seek to return to their natural, nonpolarized state. In developing a field theory approach to electrodynamics (starting in the mid-1850s), James Clerk Maxwell stops considering electric charge as a special substance that accumulates in objects, and starts to understand electric charge as a consequence of the transformation of energy in the field. This pre-quantum understanding considered magnitude of electric charge to be

4416-433: Is to reduce electrostatic repulsion inside the nucleus. Protons and neutrons are fermions , with different values of the strong isospin quantum number , so two protons and two neutrons can share the same space wave function since they are not identical quantum entities. They are sometimes viewed as two different quantum states of the same particle, the nucleon . Two fermions, such as two protons, or two neutrons, or

4512-433: The amber effect is often attributed to the ancient Greek mathematician Thales of Miletus , who lived from c. 624 to c. 546 BC, but there are doubts about whether Thales left any writings; his account about amber is known from an account from early 200s. This account can be taken as evidence that the phenomenon was known since at least c. 600 BC, but Thales explained this phenomenon as evidence for inanimate objects having

4608-448: The conventional current without regard to whether it is carried by positive charges moving in the direction of the conventional current or by negative charges moving in the opposite direction. This macroscopic viewpoint is an approximation that simplifies electromagnetic concepts and calculations. At the opposite extreme, if one looks at the microscopic situation, one sees there are many ways of carrying an electric current , including:

4704-506: The Greek word for amber ). The Latin word was translated into English as electrics . Gilbert is also credited with the term electrical , while the term electricity came later, first attributed to Sir Thomas Browne in his Pseudodoxia Epidemica from 1646. (For more linguistic details see Etymology of electricity .) Gilbert hypothesized that this amber effect could be explained by an effluvium (a small stream of particles that flows from

4800-507: The Pauli exclusion principle . Were it not for the Coulomb energy, the most stable form of nuclear matter would have the same number of neutrons as protons, since unequal numbers of neutrons and protons imply filling higher energy levels for one type of particle, while leaving lower energy levels vacant for the other type. Pairing energy . An energy which is a correction term that arises from

4896-538: The fractional quantum Hall effect . The unit faraday is sometimes used in electrochemistry. One faraday is the magnitude of the charge of one mole of elementary charges, i.e. 9.648 533 212 ... × 10  C. From ancient times, people were familiar with four types of phenomena that today would all be explained using the concept of electric charge: (a) lightning , (b) the torpedo fish (or electric ray), (c) St Elmo's Fire , and (d) that amber rubbed with fur would attract small, light objects. The first account of

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4992-407: The mass of an atom is located in the nucleus, with a very small contribution from the electron cloud . Protons and neutrons are bound together to form a nucleus by the nuclear force . The diameter of the nucleus is in the range of 1.70  fm ( 1.70 × 10  m ) for hydrogen (the diameter of a single proton) to about 11.7  fm for uranium . These dimensions are much smaller than

5088-500: The "constant" r 0 varies by 0.2 fm, depending on the nucleus in question, but this is less than 20% change from a constant. In other words, packing protons and neutrons in the nucleus gives approximately the same total size result as packing hard spheres of a constant size (like marbles) into a tight spherical or almost spherical bag (some stable nuclei are not quite spherical, but are known to be prolate ). Models of nuclear structure include: The cluster model describes

5184-401: The "optical model", frictionlessly orbiting at high speed in potential wells. In the above models, the nucleons may occupy orbitals in pairs, due to being fermions, which allows explanation of even/odd Z and N effects well known from experiments. The exact nature and capacity of nuclear shells differs from those of electrons in atomic orbitals, primarily because the potential well in which

5280-469: The IEC in 1908. The entire set of "reproducible units" was abandoned in 1948 and the "international coulomb" became the modern coulomb. Electric charge Electric charge is a conserved property : the net charge of an isolated system , the quantity of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles . In ordinary matter, negative charge

5376-620: The Molecule , that "the atom is composed of the kernel and an outer atom or shell. " Similarly, the term kern meaning kernel is used for nucleus in German and Dutch. The nucleus of an atom consists of neutrons and protons, which in turn are the manifestation of more elementary particles, called quarks , that are held in association by the nuclear strong force in certain stable combinations of hadrons , called baryons . The nuclear strong force extends far enough from each baryon so as to bind

5472-411: The amount of charge. Until 1800 it was only possible to study conduction of electric charge by using an electrostatic discharge. In 1800 Alessandro Volta was the first to show that charge could be maintained in continuous motion through a closed path. In 1833, Michael Faraday sought to remove any doubt that electricity is identical, regardless of the source by which it is produced. He discussed

5568-469: The center of an atom , discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment . After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg . An atom is composed of a positively charged nucleus, with a cloud of negatively charged electrons surrounding it, bound together by electrostatic force . Almost all of

5664-415: The charge of one helium nucleus (two protons and two neutrons bound together in a nucleus and moving around at high speeds) is the same as two deuterium nuclei (one proton and one neutron bound together, but moving much more slowly than they would if they were in a helium nucleus). Atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at

5760-464: The cork by putting thin sticks into it) showed—for the first time—that electrical effluvia (as Gray called it) could be transmitted (conducted) over a distance. Gray managed to transmit charge with twine (765 feet) and wire (865 feet). Through these experiments, Gray discovered the importance of different materials, which facilitated or hindered the conduction of electrical effluvia. John Theophilus Desaguliers , who repeated many of Gray's experiments,

5856-413: The coulomb can be modified by adding a prefix that multiplies it by a power of 10 . The coulomb is named after Charles-Augustin de Coulomb . As with every SI unit named for a person, its symbol starts with an upper case letter (C), but when written in full, it follows the rules for capitalisation of a common noun ; i.e., coulomb becomes capitalised at the beginning of a sentence and in titles but

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5952-426: The diameter of the atom itself (nucleus + electron cloud), by a factor of about 26,634 (uranium atomic radius is about 156  pm ( 156 × 10  m )) to about 60,250 ( hydrogen atomic radius is about 52.92  pm ). The branch of physics involved with the study and understanding of the atomic nucleus, including its composition and the forces that bind it together, is called nuclear physics . The nucleus

6048-599: The electric object, without diminishing its bulk or weight) that acts on other objects. This idea of a material electrical effluvium was influential in the 17th and 18th centuries. It was a precursor to ideas developed in the 18th century about "electric fluid" (Dufay, Nollet, Franklin) and "electric charge". Around 1663 Otto von Guericke invented what was probably the first electrostatic generator , but he did not recognize it primarily as an electrical device and only conducted minimal electrical experiments with it. Other European pioneers were Robert Boyle , who in 1675 published

6144-414: The electromagnetic forces that hold the parts of the atoms together internally (for example, the forces that hold the electrons in an inert gas atom bound to its nucleus). The nuclear force is highly attractive at the distance of typical nucleon separation, and this overwhelms the repulsion between protons due to the electromagnetic force, thus allowing nuclei to exist. However, the residual strong force has

6240-410: The electrons. This is a source of confusion for beginners. The total electric charge of an isolated system remains constant regardless of changes within the system itself. This law is inherent to all processes known to physics and can be derived in a local form from gauge invariance of the wave function . The conservation of charge results in the charge-current continuity equation . More generally,

6336-541: The first book in English that was devoted solely to electrical phenomena. His work was largely a repetition of Gilbert's studies, but he also identified several more "electrics", and noted mutual attraction between two bodies. In 1729 Stephen Gray was experimenting with static electricity , which he generated using a glass tube. He noticed that a cork, used to protect the tube from dust and moisture, also became electrified (charged). Further experiments (e.g., extending

6432-431: The foil should act as electrically neutral if the negative and positive charges are so intimately mixed as to make it appear neutral. To his surprise, many of the particles were deflected at very large angles. Because the mass of an alpha particle is about 8000 times that of an electron, it became apparent that a very strong force must be present if it could deflect the massive and fast moving alpha particles. He realized that

6528-534: The force is proportional to the product of their charges, and inversely proportional to the square of the distance between them. The charge of an antiparticle equals that of the corresponding particle, but with opposite sign. The electric charge of a macroscopic object is the sum of the electric charges of the particles that it is made up of. This charge is often small, because matter is made of atoms , and atoms typically have equal numbers of protons and electrons , in which case their charges cancel out, yielding

6624-407: The glass tube and participant B receive a shock to the knuckle from the charged tube. Franklin identified participant B to be positively charged after having been shocked by the tube. There is some ambiguity about whether William Watson independently arrived at the same one-fluid explanation around the same time (1747). Watson, after seeing Franklin's letter to Collinson, claims that he had presented

6720-612: The material, rigidly bound in place, giving an overall net positive or negative charge to the object. Also, macroscopic objects made of conductive elements can more or less easily (depending on the element) take on or give off electrons, and then maintain a net negative or positive charge indefinitely. When the net electric charge of an object is non-zero and motionless, the phenomenon is known as static electricity . This can easily be produced by rubbing two dissimilar materials together, such as rubbing amber with fur or glass with silk . In this way, non-conductive materials can be charged to

6816-430: The neutrons and protons together against the repulsive electrical force between the positively charged protons. The nuclear strong force has a very short range, and essentially drops to zero just beyond the edge of the nucleus. The collective action of the positively charged nucleus is to hold the electrically negative charged electrons in their orbits about the nucleus. The collection of negatively charged electrons orbiting

6912-421: The noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows tin to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 ( technetium ) and 61 ( promethium ), each of which

7008-427: The nucleons move (especially in larger nuclei) is quite different from the central electromagnetic potential well which binds electrons in atoms. Some resemblance to atomic orbital models may be seen in a small atomic nucleus like that of helium-4 , in which the two protons and two neutrons separately occupy 1s orbitals analogous to the 1s orbital for the two electrons in the helium atom, and achieve unusual stability for

7104-457: The nucleus as a molecule-like collection of proton-neutron groups (e.g., alpha particles ) with one or more valence neutrons occupying molecular orbitals. Early models of the nucleus viewed the nucleus as a rotating liquid drop. In this model, the trade-off of long-range electromagnetic forces and relatively short-range nuclear forces, together cause behavior which resembled surface tension forces in liquid drops of different sizes. This formula

7200-412: The nucleus display an affinity for certain configurations and numbers of electrons that make their orbits stable. Which chemical element an atom represents is determined by the number of protons in the nucleus; the neutral atom will have an equal number of electrons orbiting that nucleus. Individual chemical elements can create more stable electron configurations by combining to share their electrons. It

7296-567: The nucleus of uranium-238 ). These nuclei are not maximally dense. Halo nuclei form at the extreme edges of the chart of the nuclides —the neutron drip line and proton drip line—and are all unstable with short half-lives, measured in milliseconds ; for example, lithium-11 has a half-life of 8.8 ms . Halos in effect represent an excited state with nucleons in an outer quantum shell which has unfilled energy levels "below" it (both in terms of radius and energy). The halo may be made of either neutrons [NN, NNN] or protons [PP, PPP]. Nuclei which have

7392-468: The object (e.g., due to an external electromagnetic field , or bound polar molecules). In such cases, the object is said to be polarized . The charge due to polarization is known as bound charge , while the charge on an object produced by electrons gained or lost from outside the object is called free charge . The motion of electrons in conductive metals in a specific direction is known as electric current . The SI unit of quantity of electric charge

7488-490: The other kind must be considered as a matter of arbitrary convention—just as it is a matter of convention in mathematical diagram to reckon positive distances towards the right hand. Electric current is the flow of electric charge through an object. The most common charge carriers are the positively charged proton and the negatively charged electron . The movement of any of these charged particles constitutes an electric current. In many situations, it suffices to speak of

7584-414: The other. He came to the conclusion that electric charge was a relation between two or more bodies, because he could not charge one body without having an opposite charge in another body. In 1838, Faraday also put forth a theoretical explanation of electric force, while expressing neutrality about whether it originates from one, two, or no fluids. He focused on the idea that the normal state of particles

7680-461: The particle that we now call the electron in 1897. The unit is today referred to as elementary charge , fundamental unit of charge , or simply denoted e , with the charge of an electron being − e . The charge of an isolated system should be a multiple of the elementary charge e , even if at large scales charge seems to behave as a continuous quantity. In some contexts it is meaningful to speak of fractions of an elementary charge; for example, in

7776-460: The plum pudding model could not be accurate and that the deflections of the alpha particles could only be explained if the positive and negative charges were separated from each other and that the mass of the atom was a concentrated point of positive charge. This justified the idea of a nuclear atom with a dense center of positive charge and mass. The term nucleus is from the Latin word nucleus ,

7872-472: The proton and neutron potential wells. While each nucleon is a fermion, the {NP} deuteron is a boson and thus does not follow Pauli Exclusion for close packing within shells. Lithium-6 with 6 nucleons is highly stable without a closed second 1p shell orbital. For light nuclei with total nucleon numbers 1 to 6 only those with 5 do not show some evidence of stability. Observations of beta-stability of light nuclei outside closed shells indicate that nuclear stability

7968-521: The rate of change in charge density ρ within a volume of integration V is equal to the area integral over the current density J through the closed surface S = ∂ V , which is in turn equal to the net current I : Thus, the conservation of electric charge, as expressed by the continuity equation, gives the result: The charge transferred between times t i {\displaystyle t_{\mathrm {i} }} and t f {\displaystyle t_{\mathrm {f} }}

8064-438: The residual strong force ( nuclear force ). The residual strong force is a minor residuum of the strong interaction which binds quarks together to form protons and neutrons. This force is much weaker between neutrons and protons because it is mostly neutralized within them, in the same way that electromagnetic forces between neutral atoms (such as van der Waals forces that act between two inert gas atoms) are much weaker than

8160-526: The rubbed surfaces in contact, they still exhibit no electrical properties. When separated, they attract each other. A second piece of glass rubbed with a second piece of resin, then separated and suspended near the former pieces of glass and resin causes these phenomena: This attraction and repulsion is an electrical phenomenon , and the bodies that exhibit them are said to be electrified , or electrically charged . Bodies may be electrified in many other ways, as well as by sliding. The electrical properties of

8256-535: The same explanation as Franklin in spring 1747. Franklin had studied some of Watson's works prior to making his own experiments and analysis, which was probably significant for Franklin's own theorizing. One physicist suggests that Watson first proposed a one-fluid theory, which Franklin then elaborated further and more influentially. A historian of science argues that Watson missed a subtle difference between his ideas and Franklin's, so that Watson misinterpreted his ideas as being similar to Franklin's. In any case, there

8352-424: The same reason. Nuclei with 5 nucleons are all extremely unstable and short-lived, yet, helium-3 , with 3 nucleons, is very stable even with lack of a closed 1s orbital shell. Another nucleus with 3 nucleons, the triton hydrogen-3 is unstable and will decay into helium-3 when isolated. Weak nuclear stability with 2 nucleons {NP} in the 1s orbital is found in the deuteron hydrogen-2 , with only one nucleon in each of

8448-466: The start of ongoing qualitative and quantitative research into electrical phenomena can be marked with the publication of De Magnete by the English scientist William Gilbert in 1600. In this book, there was a small section where Gilbert returned to the amber effect (as he called it) in addressing many of the earlier theories, and coined the Neo-Latin word electrica (from ἤλεκτρον (ēlektron),

8544-424: The sum of five types of energies (see below). Then the picture of a nucleus as a drop of incompressible liquid roughly accounts for the observed variation of binding energy of the nucleus: [REDACTED] Volume energy . When an assembly of nucleons of the same size is packed together into the smallest volume, each interior nucleon has a certain number of other nucleons in contact with it. So, this nuclear energy

8640-400: The tendency of proton pairs and neutron pairs to occur. An even number of particles is more stable than an odd number. A number of models for the nucleus have also been proposed in which nucleons occupy orbitals, much like the atomic orbitals in atomic physics theory. These wave models imagine nucleons to be either sizeless point particles in potential wells, or else probability waves as in

8736-410: The two pieces of glass are similar to each other but opposite to those of the two pieces of resin: The glass attracts what the resin repels and repels what the resin attracts. If a body electrified in any manner whatsoever behaves as the glass does, that is, if it repels the glass and attracts the resin, the body is said to be vitreously electrified, and if it attracts the glass and repels the resin it

8832-450: The volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one watt of power. The coulomb (later "absolute coulomb" or " abcoulomb " for disambiguation) was part of the EMU system of units. The "international coulomb" based on laboratory specifications for its measurement was introduced by

8928-419: Was previously defined in terms of the force between two wires. The coulomb was originally defined, using the latter definition of the ampere, as 1 A × 1 s . The 2019 redefinition of the ampere and other SI base units fixed the numerical value of the elementary charge when expressed in coulombs and therefore fixed the value of the coulomb when expressed as a multiple of the fundamental charge. One coulomb

9024-417: Was discovered in 1911, as a result of Ernest Rutherford 's efforts to test Thomson's " plum pudding model " of the atom. The electron had already been discovered by J. J. Thomson . Knowing that atoms are electrically neutral, J. J. Thomson postulated that there must be a positive charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within

9120-407: Was no animosity between Watson and Franklin, and the Franklin model of electrical action, formulated in early 1747, eventually became widely accepted at that time. After Franklin's work, effluvia-based explanations were rarely put forward. It is now known that the Franklin model was fundamentally correct. There is only one kind of electrical charge, and only one variable is required to keep track of

9216-511: Was not inseparably connected to the bodies that were electrified by rubbing. In 1733 Charles François de Cisternay du Fay , inspired by Gray's work, made a series of experiments (reported in Mémoires de l' Académie Royale des Sciences ), showing that more or less all substances could be 'electrified' by rubbing, except for metals and fluids and proposed that electricity comes in two varieties that cancel each other, which he expressed in terms of

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