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
Ground loop (electricity) the cable If a current "I" from a separate source is flowing through the ground conductor, the resistance "R" of the conductor will create a voltage drop along the cable ground of "IR", so the destination end of the ground conductor will be at a different potential than the source end Since the differential amplifier has high impedance, little current flows in the signal wire, therefore there is no voltage drop across it: formula_15 The ground voltage appears to be in series with the signal voltage "V" and adds to it If "I" is an AC current this can result