An array is a special variable, which can hold more than one value at a time. If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
milliamps or watt/volt. The SI base unit for electric current is the ampere. 1 ampere is equal to 1000 milliamps, or 1 watt/volt. Note that rounding errors may occur, so always check the results. Use this page to learn how to convert between milliamperes and watts/volt. Type in your own numbers in the form to convert the units!
A watt is an amount of energy per second, or Joules per second (1 W = 1 J/s). The number of watts is for an electrical circuit given by the number of amperes times the voltage drop: 1 W = 1 V * 1 A. A power company supplying electricity wants to know how much energy (that's Joules) you have used.