Automobiles are one of the most important inventions in modern times. They play a major role in our daily life and are a lifeline for many of us. They help us to go about our lives without having to walk everywhere or have other people do it for us. They also provide us with the luxury of travelling long distances at very high speeds. Automobiles are also used for a wide variety of other tasks such as travelling to work or school, shopping and visiting friends and relatives.
A car or automobile is a wheeled motor vehicle designed to run primarily on roads and seat one to seven passengers. The term is most commonly applied to vehicles that have four wheels and are powered by an internal combustion engine fueled with gasoline, diesel or kerosene. However, there are a number of other fuels which may be used to power an automobile including electricity, natural gas, LPG (liquefied petroleum gas) and steam.
The engines in most automobiles are based on the Otto cycle of internal combustion with four or more cylinders. Each cylinder has its own combustion chamber and is ignited by a spark plug connected to the crankshaft. The resulting explosion drives the piston down, and the power generated is transferred through the transmission system to turn the wheels.
The traction provided by the road is determined by the torque of the engine and the resistance offered by the road surface, the weather conditions and other factors. The transmission systems in most cars allow the driver to choose between different gear ratios to increase or decrease the tractive effort when necessary. Other essential systems include the braking system to stop the automobile when needed, and the chassis which holds all these components together.