as both are linear models relating flux and potential in their respective systems. Common voltages The voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell (see ). Cells can be combined in series for multiples of that voltage, or additional circuitry added to adjust the voltage to a different level. Mechanical generators can usually be constructed to any voltage in a range of feasibility. Nominal voltages of familiar sources: Nerve cell resting potential: ~75 mV Single-cell, rechargeable NiMH or NiCd battery: 1.2 V Single-cell, non-rechargeable (e.g., AAA, AA, C and D cells): alkaline battery: 1.5 V; zinc–carbon battery: 1.56 V if fresh and unused LiFePO4 rechargeable battery: 3.3 V Cobalt-based lithium polymer rechargeable battery: 3.75 V (see Comparison of commercial battery types) Transistor-transistor logic/CMOS (TTL) power supply: 5 V USB: 5 V DC PP3 battery: 9 V Automobile battery systems are 2.1 volts per cell; a "12 V" battery is 6 cells, or 12.6 V; a "24 V" battery is 12 cells, or 25.2 V. Some antique vehicles use "6 V" 3-cell batteries, or 6.3 volts. Household mains electricity AC: (see List of countries with mains power plugs, voltages and frequencies) 100 V in Japan, 120 V in North America, 230 V in Europe, Asia, Africa and Australia Rapid transit third rail: 600–750 V (see List of railway electrification systems) High-speed train overhead power lines: 25 kV at 50 Hz, but see the List of railway electrification systems and 25 kV at 60 Hz for exceptions. High-voltage electric power transmission lines: 110 kV and up (1.15 MV is the record; the highest active voltage is 1.10 MV) Lightning: a maximum of around 150 MV. History In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In 1861, Latimer Clark and Sir Charles Bright coined the name "volt" for the unit of resistance. By 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force. They made the volt equal to 108 cgs units