Engine of cars
An engine and motor are machines designed
to convert energy
into useful mechanical motion.[1][2] Heat
engines, including internal combustion engines and external combustion engines (such as steam
engines) burn a fuel
to create heat,
which then creates motion. Electric motors convert electrical energy into mechanical motion, pneumatic
motors use compressed air and others—such as clockwork
motors in wind-up toys—use elastic
energy. In biological systems, molecular
motors, like myosins in muscles, use "Engine" was originally a term for any
mechanical device that converts force into motion. Hence, pre-industrial
weapons such as catapults,
trebuchets
and battering
rams were called "siege engines". The word "gin," as in
"cotton
gin", is short for "engine." The word derives from Old French
engin, from the Latin ingenium, which is also the root of the word ingenious.
Most mechanical devices invented during the industrial revolution were described as
engines—the steam engine being a notable example.
In modern usage, the term engine typically describes devices, like
steam engines and internal combustion engines, that burn or otherwise consume
fuel to perform mechanical work by exerting a torque or linear
force to drive machinery that generates electricity,
pumps water, or compresses
gas. In the context of propulsion systems, an air-breathing engine is one
that uses atmospheric air to oxidise the fuel rather
than supplying an independent oxidizer, as in a rocket.
When the internal combustion engine was invented, the term "motor"
was initially used to distinguish it from the steam engine—which was in wide
use at the time, powering locomotives and other vehicles such as steam rollers.
"Motor" and "engine" later came to be used interchangeably
in casual discourse. However, technically, the two words have different
meanings. An engine is a device that burns or
otherwise consumes fuel, changing its chemical composition, whereas a motor is
a device driven by electricity, which does not change the chemical composition
of its energy source.[3]
A heat engine may also serve as a prime
mover—a component that transforms the flow or changes in pressure of a fluid
into mechanical energy.[4] An automobile
powered by an internal combustion engine may make use of various motors and
pumps, but ultimately all such devices derive their power from the engine.
Another way of looking at it is that a motor receives power from an external
source, and then converts it into mechanical energy, while an engine creates
power from pressure (derived directly from the explosive force of combustion or
other chemical
reaction, or secondarily from the action of some such force on other substances
such as air, water, or steam).[5]
Devices converting heat energy into motion are commonly referred to simply
as engines
chemical energy to create motion.