The unit of energy in the International System of Units (SI) is the joule (J). One joule is defined as the amount of energy transferred when a force of one newton moves an object one meter in the direction of the force. In SI base units, it is expressed as 1 J=1 kg⋅m2/s21,\text{J}=1,\text{kg}\cdot \text{m}^2/\text{s}^21J=1kg⋅m2/s2

. Besides the joule, other units of energy include:

• The electronvolt (eV) , commonly used in atomic and particle physics, where 1 eV=1.602176634×10−19 J1,\text{eV}=1.602176634\times 10^{-19},\text{J}1eV=1.602176634×10−19J

• The kilowatt-hour (kWh) , often used in energy consumption, where 1 kWh=3.6×106 J1,\text{kWh}=3.6\times 10^6,\text{J}1kWh=3.6×106J

• The British thermal unit (BTU) , used in imperial and US customary systems, approximately equal to 1055 joules

The joule is named after James Prescott Joule, who contributed significantly to the concept of energy