The measured value of the elementary charge is approximately (1.602 176 487 ± 0.000 000 040) × 10 -19 coulombs or 4.8 × 10 −19 statcoulombs in cgs units. The elementary charge is also the electrical charge carried by a proton, however with opposite polarity. In other words, protons have a positive e charge, whereas electrons have a negative e charge. In order to avoid confusion on the sign, e is normally considered as a positive elementary charge. In systems of units other than SI such as cgs, electric charge is expressed as combination of only three fundamental quantities (length, mass, and time), and not four, as in SI, where electric charge is a combination of length, mass, time, and electric current.The elementary charge is usually represented by e. One faraday of charge is the magnitude of the charge of one mole of electrons, i.e. The unit faraday is sometimes used in electrochemistry. In some contexts it is meaningful to speak of fractions of a charge for example in the charging of a capacitor, or in the fractional quantum Hall effect. A measure of charge should be a multiple of the elementary charge e, even if at large scales charge seems to behave as a real quantity. The unit is today treated as nameless, referred to as "elementary charge", "fundamental unit of charge", or simply as "e". This was before the discovery of the particle by J.J. The quantity of electric charge can be directly measured with an electrometer, or indirectly measured with a ballistic galvanometer.Īfter finding the quantized character of charge, in 1891 George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. The symbol Q is often used to denote a quantity of electricity or charge. The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second. Hence, the charge of an electron is approximately −1.602×10 −19 C. The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×10 18 e (e is the charge of a proton). All else being equal, the more charge a particle has, the more it curves (i.e., the tighter the curve). For instance, a proton curves the opposite way that an electron does. Scientists measure the charge on particles by measuring how they curve when the travel in a magnetic field. Things that have different charges attract each other. Things with the same charge repel each other. Things that have more electrons than protons are negatively charged, while things with fewer electrons than protons are positively charged. Things that have equal numbers of electrons and protons are neutral. The law that describes how strongly charges pull and push on each other is called Coulomb's Law. It was discovered by Charles-Augustin de Coulomb. Things that have the same charge push each other away (they repel each other). This makes electrons and protons stick together to form atoms. Things that are negatively charged and things that are positively charged pull on (attract) each other. Electrons are negatively charged while protons are positively charged. ELECTRIC CHARGE UNIT MEASUREMENTElectric charge is a basic property of electrons, protons and other subatomic particles.
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