Energy Unit Conversion

Because energy is one of the most important quantities, there are many energy units which often creates confusion. Throughout this book, we used the SI units for all physical quantities. The SI unit of energy is joule, defined as the energy capable of pushing an object with one newton of force by one meter:

J = N • m. (A.1)

The basic SI unit of power, the watt, equals one joule per second,

Подпись: (A.2)W = J/s.

The most frequently used units of energy and power are listed in Table A.1.

Electrical power is the product of the current in amperes and voltage in volts:

W = A • V. (A.3)

Utility companies often use an energy unit derived from electrical power, the kilowatt- hour, or kWh:

1 kWh = 3600 kJ = 3.6 MJ. (A.4)

Table A.1: Energy and Power Units

Name

Symbol

Equals

Kilojoule

kJ

103 J

Megajoule

MJ

106 J

Gigajoule

GJ

109 J

Etajoule

EJ

1018 J

Kilowatt

kW

103 W

Megawatt

MW

106 W

Gigawatt

GW

109 W

Terawatt

TW

1012 W

Updated: August 24, 2015 — 7:49 am