<P> Even when an object's net charge is zero, charge can be distributed non-uniformly in 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 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 . </P> <P> The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 7018624200000000000 ♠ 6.242 × 10 e (e is the charge of a proton). Hence, the charge of an electron is approximately 3018839800000000000 ♠ − 1.602 × 10 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 . </P> <P> 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 . </P> <P> 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 . </P>

Who measured the magnitude of the positive charge on the nucleus