ELECTRIC-CHARGE Units Conversion

ELECTRIC CHARGE UNIT MEASUREMENT

Electric charge is a basic property of electrons, protons and other subatomic particles. Electrons are negatively charged while protons are positively charged. Things that are negatively charged and things that are positively charged pull on (attract) each other. This makes electrons and protons stick together to form atoms. Things that have the same charge push each other away (they repel each other). This is called the Law of Charges. It was discovered by Charles-Augustin de Coulomb. The law that describes how strongly charges pull and push on each other is called Coulomb's Law.

Things that have equal numbers of electrons and protons are neutral. Things that have more electrons than protons are negatively charged, while things with fewer electrons than protons are positively charged. Things with the same charge repel each other. Things that have different charges attract each other.

Scientists measure the charge on particles by measuring how they curve when the travel in a magnetic field. For instance, a proton curves the opposite way that an electron does. A neutron does not curve at all. All else being equal, the more charge a particle has, the more it curves (i.e., the tighter the curve).

The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×10¹⁸ e (e is the charge of a proton). Hence, the charge of an electron is approximately −1.602×10⁻¹⁹ C. 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. The symbol Q is often used to denote a quantity of electricity or charge. The quantity of electric charge can be directly measured with an electrometer, or indirectly measured with a ballistic galvanometer.

After finding the quantized character of charge, in 1891 George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. This was before the discovery of the particle by J.J. Thomson in 1897. The unit is today treated as nameless, referred to as "elementary charge", "fundamental unit of charge", or simply as "e". 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. 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.

The unit faraday is sometimes used in electrochemistry. One faraday of charge is the magnitude of the charge of one mole of electrons, i.e. 96485.33289(59) C.

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.