Energy cannot be created nor destroyed,
but it can be converted from one form to another.

• Engineers design energy conversion systems to change input energy into a different form of output energy.

• Example: A car engine converts chemical energy (fuel) into mechanical energy (motion).

• In every system, some energy changes into less useful forms because of:

  • Resistance – opposition to the flow of electricity in wires or circuits.

  • Friction – rubbing between surfaces that produces heat.

• These less useful forms of energy are sometimes called energy losses (for example, heat instead of motion).

• To reduce losses, engineers work to improve efficiency – getting the most useful output from the least amount of input.

Examples of energy

• Motion

• Electrical

• Thermal

Kinetic

• Gravitational

• Elastic

• Chemical (electrons)

Potential

Efficiency

When energy is converted from one type to another, the goal is to maximize the efficiency of that process.
For example, most electric power plants have an efficiency of around 30%. The rest of the energy is often lost through the smokestack as thermal energy. However, some power plants follow a process called cogenerating(opens in a new tab), where the system captures this thermal energy and uses it to heat a building

Work

Work (symbol W) is the energy transferred when a force, F, is applied to an object moving through a distance, d.
Work is done only by the component of force parallel to the distance the object moves, F_II.

Power

Power (symbol P) is the rate at which work (W) is performed in a given time (t). 
Power is found in various forms: 

• Electrical power uses electrical energy to do work. 

• Mechanical power uses mechanical energy to do work. 

• Fluid power uses energy transferred by liquids (hydraulic) and gases (pneumatic) to do work.