Automobiles are vehicles used for transportation of passengers. They have four to eight wheels & powered by internal combustion engine (which usually runs on gasoline) that turns the wheels through the transmission system. Its auxiliary parts like muffler, radiator, fuel pump, air conditioning & ignition systems work together to make the car move. Various definitions have emerged for what constitutes an automobile, but most agree it is a motor vehicle designed primarily for passenger transport. It is a major mode of land transportation in the developed world, with over one billion cars worldwide. The branches of engineering that deal with the manufacture and technologies of automobiles are called automotive engineering.
It is not easy to imagine modern life without the automobile. As early as 1920 the automobile became the backbone of a new consumer goods-oriented society. It ranked first in the value of manufactured products and was the largest customer of many ancillary industries, especially steel and petroleum. It became the primary means of family travel, with Americans driving over three trillion miles (five trillion kilometres) per year on average. It is also responsible for a revolution in industrial manufacturing. American automaker Henry Ford introduced the concept of assembly lines and made his Model T affordable for middle-class families.
The social effects of the automobile were equally dramatic. Urban dwellers could rediscover pristine countryside, and rural residents found shopping opportunities in towns. In addition, teenagers gained independence with their own cars. Couples could spend quality time alone in their automobiles, and relaxed sexual attitudes were encouraged by the mobility of the automobile.