To learn how power is transferred in a vehicle, key terms (force, work, power, and energy) and the relationship between them need to be studied.
Force
Simply defined, force is a push or pull interaction between objects. This interaction can occur when objects are in physical contact with one another or when there is an action at a distance caused by magnetic forces, gravitational forces, and electric forces.
Work
When an object has moved from a force, the position of the object has changed and work has occurred. If no motion has occurred, no work has been done. Work is the transfer of energy from one object to another.
Power
Power is the rate at which work is done (the amount of work done, energy delivered, in a given amount of time).
Power = Work/Time
Energy
Objects have the ability to do work when they have energy. Different forms of energy are classified into two categories: potential and kinetic. Potential energy is stored energy or energy of position. Kinetic energy is the energy of an object from its movement. Energy is required to do work. Gasoline, diesel, electricity, or some other source of energy is needed for a vehicle to do work. Energy and power are linked, but are not the same thing. This is helpful to know when looking at battery ratings on hybrid and electric vehicles. These batteries are usually rated in kilowatt hours (kWh).
Energy = Power x Time
1 kWh = 1 kilowatt x 1 hour
For example, an electric vehicle might have a battery capacity of 60 kWh. Think of energy as the amount of “fuel” stored or used to perform work.