Energy

There are many forms of energy, such as heat, mechanical, electrical, radiant, chemical, and nuclear energies. Energy is measured in such units as the joule (J), erg, kilowatt-hour (kW-hr), kilocalorie (kcal), foot-pound (ft-lb.), electron-volt (ev), and British thermal unit (BTU). Energy comes in different forms – heat (thermal), light (radiant), mechanical, electrical, chemical, and nuclear. There are two types of energy – stored (potential) energy and working (kinetic) energy. For example, the energy from the food that you eat is stored in your body as chemical energy until you use it. Much of the energy we use comes from non-renewable sources such as fossil fuels (coal, oil and gas). Renewable energy sources include solar power, wind power and hydroelectric power.