Electric current metal (ideal) resistor (or other ohmic device): where formula_6 is the current, measured in amperes; formula_26 is the potential difference, measured in volts; and formula_27 is the resistance, measured in ohms. For alternating currents, especially at higher frequencies, skin effect causes the current to spread unevenly across the conductor cross-section, with higher density near the surface, thus increasing the apparent resistance. The mobile charged particles within a conductor move constantly in random directions, like the particles of a gas. (More accurately, a Fermi gas.) To create a net flow of charge, the particles must also move together with an average
Ohm and the CGS unit. Although called "legal", this standard was not adopted by any national legislation. The "international" ohm was recommended by unanimous resolution at the International Electrical Congress 1893 in Chicago. The unit was based upon the ohm equal to 10 units of resistance of the C.G.S. system of electromagnetic units. The International Ohm is represented by the resistance offered to an unvarying electric current in a mercury column of constant cross-sectional area 106.3 cm long of mass 14.4521 grams and 0 °C This definition became the basis for the legal definition of the ohm in several countries. In