Common Electrical Terms, Abbreviations and Definitions lumen (lm)Practical Definition: This is a measurement of how bright a light source is rated. Really not a good practical measurement. An example is when you purchase a 100-watt light bulb. Watt is the power consumed, not a measurement of light, but we all know that a 100-watt light bulb is pretty bright. Used to compare two light sources to one another. See Lux definition below. Technical Definition: The lumen (symbolized lm) is the International Unit of luminous flux. A unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candela (see definition below) intensity. lux (lx) Practical Definition: Lux is the amount of light you actually see. One lux is equal to one lumen per square meter. It is the amount of light cast on a surface. This is the most practical measurement of light. See the chart below for examples:

Illuminance Abbreviation Pronunciation Example 0.00005 lux 50 lx 50 micro-lux Starlight 0.0001 lux 100 lx 100 micro-lux Moonless overcast night sky 0.001 lux 1 mlx 1 milli-lux Moonless clear night sky 0.01 lux 10 mlx 10 milli-lux Quarter Moon 0.25 lux 250 mlx 250 milli-lux Full Moon on a clear night 1 lux 1 lx 1 lux Moonlight at high altitude at tropical latitudes 10 lux 10 lx 10 lux Candle at a distance of 1 ft 50 lux 50 lx 50 lux Family living room 80 lux 80 lx 80 lux Hallway/Toilet 400 lux 400 lx 400 lux A brightly lit office 400 lux 400 lx 400 lux Sunrise or sunset on a clear day 1000 lux 1 klx 1 kilo-lux Typical TV studio lighting 32000 lux 32 klx 32 kilo-lux Sunlight on an average day (min.) 100000 lux 100 klx 100 kilo-lux Sunlight on an average day (max.)

Engineering Definition: The lux (symbol: lx) is the unit of illuminance and luminous emittance. It is used in photometry as a measure of the intensity of light, with wavelengths weighted according to the luminosity function, a standardized model of human brightness perception. It is used as a measure of the intensity of light. In English, "lux" is used in both singular and plural. 1 lux = 1 lumen/sq. meter. foot-candle (fc) Practical Definition: In practical applications, as when measuring room illumination, it is very difficult to measure illuminance more accurately than 10%, and for many purposes it is quite sufficient to think of one foot-candle as about ten lux. Therefore, it is commonplace to simply state 1 fc = 10 lux. Technical Definition: One foot-candle 10.764 lux. The foot-candle (or lumen per square foot) is a non-SI unit of illuminance. It is obsolete but it is still in fairly common use in the United States, particularly in construction-related engineering and in building codes. Because lux and foot-candles are different units of the same quantity, it is perfectly valid to convert foot-candles to lux and vice versa.

Common Electrical Terms, Abbreviations and Definitionspg 2 The name "foot-candle" conveys "the illuminance cast on a surface by a one-candela source one foot away. As natural as this sounds, this style of name is now frowned upon, because the dimensional formula for the unit is not foot candela, but lumen/sq ft. Some sources do however note that the "lux" can be thought of as a "meter-candle" (i.e. the illuminance cast on a surface by a one-candela source one meter away). A source that is farther away provides less illumination than one that is close, so one lux is less illuminance than one foot-candle. Since illuminance follows the inverse-square law, and since one foot = 0.3048 m, one lux = 0.30482 foot-candle 1/10.764 foot-candle. ampere (amp or A) Practical Definition: The ampere, in practice often shortened to amp, is a unit of electric current, or amount of electric charge per second. Technical Definition: The base unit of electric current in the International System of Units that is equal to a constant current which when maintained in two straight parallel conductors of infinite length and negligible circular sections one meter apart in a vacuum produces between the conductors a force equal to 2 107 newton per meter of length. amperehour (Amp-Hours or Ah) Practical Definition: A unit of measure to describe how long a battery will run. For example, a 12 Ah battery will run for 12 hours with a 1 amp load on it, or 6 hours with a 2 amp load on it, or 3 hours with a 4 amp load on it, and so on. Technical Definition: A unit quantity of electricity equal to the quantity carried past any point of a circuit in one hour by a steady current of one ampere. Light Emitting Diode (LED) Practical Definition: A very small light source used in electronics. Technical Definition: A semiconductor diode that emits light when a voltage is applied to it and that is used especially in electronic devices (as for an indicator light). watt (W) Practical Definition: A unit of power, often incorrectly associated with light output. 1 Watt = 1 Volt x 1 Amp Technical Definition: The watt (symbol: W) is the SI derived unit of power, equal to one joule of energy per second. That is, if 1 volt of potential difference is applied to a resistive load, and a current of 1 ampere flows, then 1 watt of power is dissipated.

Common Electrical Terms, Abbreviations and Definitionspg 3 volt (V) Practical Definition: Volt is used to quantify the electrical potential of an electrical source. See list below for common examples: Nominal voltages of familiar sources:

Nerve cell action potential: around 75 mV Single-cell, rechargeable NiMH or NiCd battery: 1.2 V Mercury battery: 1.355 V Single-cell, non-rechargeable alkaline battery (e.g. AAA, AA, C and D cells): 1.5 V Lithium polymer rechargeable battery: 3.75 V Automobile electrical system: "12 V", about 11.8 V discharged, 12.8 V charged, and 13.8-

14.4 V while charging (vehicle running). Household mains electricity: 120 V in North America Rapid transit third rail: 600 to 750 V High speed train overhead power lines: 25 kV (kilo-volt) High voltage electric power transmission lines: 110 kV (kilo-volt) Lightning: Varies greatly, often around 100 MV (mega-volt)

Technical Definition: The unit of electrical potential difference and electromotive force equal to the difference of potential between two points in a conducting wire carrying a constant current of one ampere when the power dissipated between these two points is equal to one watt and equivalent to the potential difference across a resistance of one ohm when one ampere is flowing through it Rated Power: the maximum amount of wattage (W) the solar panel is rated for Peak Power: the maximum amount of power in watts (W) the solar panel will produce Peak Power Voltage: the maximum amount of voltage (V) or power the solar panel will produce Peak Power Current: the maximum amount of current in amps (A) that the solar panel will produce Open Circuit Voltage: a short spike in voltage (V) that is not sustained over a period of time Short Circuit Current: a short spike in amps (A) that is not sustained over a period of time UV: (Ultra Violet) beyond the visible spectrum at its violet end -- used of radiation having a wavelength shorter than wavelengths of visible light and longer than those of X-rays