Surface resistance to relative motion, which slows down movement and causes heat. FUEL CELL . The electrical process causes hydrogen atoms to give up their electrons. It does not, however, store energy as a battery does. Fuel cells can be used in stationary applications like generating electricity or heating buildings, and for powering vehicles, buses and trains.
Fuel cells are at least twice as efficient as gasoline engines.
The ratio of heat produced by a fuel for doing work to the available heat of the fuel.