Automobiles, also known as motorcars, are four-wheeled vehicles designed primarily for passenger transportation and powered by an internal combustion engine using a volatile fuel. They are one of the most universal of modern technologies and one of the world’s largest industries, with production exceeding 73 million in 2017. The automobile revolutionized life in the United States by offering a means of personal mobility that few could previously afford. It led to development of better roads and highways, stimulated participation in outdoor recreation, spurred the growth of tourism-related businesses such as roadside restaurants and motels, and helped end rural isolation by bringing city services such as schools and medical care to suburban areas. It also created jobs in factories producing automotive parts and components and in service stations and convenience stores that sold gas and other supplies.
The scientific and technical building blocks for the automobile date back several hundred years, but it was Henry Ford who made it affordable to most Americans. He developed mass-production techniques for car manufacturing and established the “Big Three” automobile manufacturers, which became a global enterprise by the 1920s. In addition, he introduced the practice of using common mechanical parts for different models and price levels within a company, which enabled buyers to “move up” in cars as their incomes increased.
Today’s automobiles feature sophisticated mechanical systems with many subsystems, each with specific design functions. For example, the ignition system controls the timing of when the engine starts and stops. The engine uses a spark plug to ignite the air and fuel mixture in the combustion chamber to create electricity, which powers the drive train, brakes and transmission. The engine may use a gaseous or liquid fuel such as gasoline, kerosene or propane. The automobile can also be a hybrid, with an electric motor that provides acceleration and recharging for the battery, or a pure-electric vehicle with no internal combustion engine.
The engine is located in the front of the automobile, over or ahead of the front axle. It is weighted in this configuration so that the automobile’s center of gravity is low. In contrast, trucks and buses (or omnibuses or coaches) are designed to carry more cargo than passengers, and their center of gravity is higher because they have much heavier bodies. Some cars are rear-engined, with the engine behind the rear axle. This configuration has a lower center of gravity but requires more complex mechanical systems to ensure safe operation. Some manufacturers use mid-engine configurations, with the engine in between the front and rear axles. This allows for more interior space but raises the cost of manufacture because the chassis must be designed to support the heavier engine and gearbox. Nevertheless, the advantages of owning an automobile outweigh the initial expense and maintenance costs. Many people cannot live without the freedom that a car offers. They can go to work earlier or later than others, visit friends in different parts of the city and not have to depend on public transportation schedules.