If you look around you, you will for sure find examples of complex machines at work. Just look at your stapler on your desk. That’s a complicated machine. Why? Because the definition of a complex machine is a machine made up of two or more simple machines that make your work easier to do. Take your stapler. Doesn’t this complex machine make your work of stapling a few pieces of paper together easier? Can you imagine stapling them together without the use of a stapler? You’d be standing with a little piece of wire and a hammer trying to hammer the wire through your pieces of paper. It doesn’t sound so easy. In this way, your little stapler now seems like a pretty mighty tool.

Motor engine is generally called any machine that produces a driving useful mechanical work. Such machines are of railways, ships, cars, planes, various pumps, and power generator engines. The layout of the modern engine in general is such that the movement of the so-called axis of the machine is finally achieved, from which the driving or useful work is received. All engines during their operation normally receive energy of some form e.g. thermal, electrical, or hydraulic, etc. and turn it (more accurately) into a mechanical energy or a driving project. Depending on the form of energy used by the driving machines, they are divided into:

• Thermal engines: This category includes locomotives, locomotives, gas turbines, petrol or petrol engines, gas engines, diesel engines or engines, etc.
• Hydraulic motors. In this category machines consume hydraulic energy.
• Electric motors or electric motors.

• Internal combustion is called the engines which as a means of producing a Work use the combustion of the fuel inside the engine and the Work is produced by the resulting heat gases, which have high temperature and pressure, as is the case with the petrol and diesel engines of the cars and in the airplane’s turbine.
• External combustion is called machines where combustion does not take place in the Work area, but outside it and where the means of production are not the exhausted gases, but another element such as water. This category includes steam turbines, locomotives.

Depending on how thermal energy is converted into a mechanical Work, thermal engines are distinguished in piston or reciprocating (applicable to both internal and  external combustion engines) and rotary or turbines (gas turbines are also called gas turbines  and external combustion  engines).

In particular, however, in piston -reciprocating internal combustion engines, the ignition in the cylinder can be carried out either by means of an external medium (e.g. spark), or automatically, due to high fuel compression along with the air required for combustion. Engines belonging in the first case, (the most representative engine is the Otto Engine (car engines)), are distinguished into gas and petrol engines, while in the second category diesel engines are included.

Electric motors convert mechanical energy into electrical (generators) or vice versa (engines). The operating principle is based on the production of electrokinetic forces by electromagnetic induction. For this purpose, we use the rate of change of the magnetic flow produced into one part of the machine, called inductive and imposes electromagnetic induction int other part, that takes the name inductor. Flow conversion is achieved through a rotational motion between the inductive and the inducer. The fixed part of the machine is called a stator, the mobile rotor.