In a hybrid car, the engines charge up an alternative generator when the car is running
. When the batteries of the generator have enough power stored up, the power switches from the gas engine to the generator and continues to run on the electric power supplied by the generator until it gets used up completely. When this happens, the power switched back to the gas engine which runs that car and charges up the generator again and the process continues as long as the car is running. A hybrid engine avoids emitting as many harmful emissions as a normal gas engine does because of the continuous shift of power supplying. Hybrid cars usually contain two electric motors that are attached to the front and the back wheels of the vehicle. The computer in the car controls the energy flowing to these engines according to the demands of the driver. When the driver accelerates, the computer sends more energy to increase the rotation of the wheels thus providing more torque. When the car has attained a certain speed and maintains that speed, the computer reduces the flow of energy to the motors and might even shut it down completely and the car continues to cruise.