Compressed air car The principal disadvantages are the steps of energy conversion and transmission, because each inherently has loss. For combustion engine cars, the energy is lost when chemical energy in fossil fuels is converted by the engine to mechanical energy. For electric cars, a power plant's electricity (from whatever source) is transmitted to the car's batteries, which then transmits the electricity to the car's motor, which converts it to mechanical energy. For compressed-air cars, the power plant's electricity is transmitted to a compressor, which mechanically compresses the air into the car's tank. The car's engine then converts the compressed air to mechanical
Potential energy set zero at infinity (as in the expressions given earlier in this section). A conservative force can be expressed in the language of differential geometry as a closed form. As Euclidean space is contractible, its de Rham cohomology vanishes, so every closed form is also an exact form, and can be expressed as the gradient of a scalar field. This gives a mathematical justification of the fact that all conservative forces are gradients of a potential field. Potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within