Energy Converters

Energy is the capacity to do work or produce heat — the common currency underlying every physical process. The SI base unit is the joule (J), defined as one newton of force applied over one meter. In practice, different domains use the unit most natural to their scale: mechanical engineers work in foot-pounds and joules; electricians and utilities bill in kilowatt-hours; chemists and nutritionists use calories; particle physicists use electron volts; and military analysts express explosive yields in tons of TNT. Thermal engineers use the British thermal unit (BTU) in the US and the therm for natural gas. Despite this diversity of units, all energy is interconvertible — one kilowatt-hour equals exactly 3,600,000 joules, and one dietary Calorie equals 4,186.8 joules.