With its first prototype, the Roadster, introduced in 2006, Tesla Motors ignited interest in electric cars not only as a way to save gas but as a high-performance alternative to some of the fastest sports cars. This year, Tesla started delivering production ­vehicles, based on the test car shown here. The car sells for $109,000--but costs only a couple of cents per mile to power.

1 . Electric Motor
Most electric cars have used direct-current electric motors that rely on permanent magnets. The motor in Tesla's Roadster doesn't have any magnets; instead, it uses stacks of patterned metal plates and wires that generate electromagnetic fields. Such motors, called alternating-current induction motors, were first advocated in the late 19th century by Nikola Tesla, for whom the company is named. The company picked AC induction motors because they're simple, reliable, and efficient at a wide range of speeds.