CHAPTER XXV.
ELECTRIC CARS, BOATS, AND AUTOMOBILES.
164. Electric Cars, as well as boats, automobiles, etc., etc., are moved by the power that comes from electric motors, these receiving current from the dynamos placed at some "central station." We have already seen how the motor can do many kinds of work. By properly gearing it to the car wheels, motion can be given to them which will move the car.
Fig. 237.
Fig. 237 shows two dynamos which will be supposed to be at a power house and which send out a current to propel cars. From the figure it will be seen that the wires over the cars, called trolley-wires, are connected to the positive (+) terminals of the dynamos, and that the negative (-) terminals are connected to the tracks. In case a wire were allowed to join the trolley-wire and track, we should have a short circuit, and current would not only rush back to the dynamo without doing useful work, but it would probably injure the machines. When some of the current is allowed to pass through a car, motion is produced in the motors, as has been explained. As the number of cars increases, more current passes back to the dynamos, which must do more work to furnish such current.
Trolley-poles, fastened to the top of the cars and which end in grooved wheels, called trolley-wheels, are pressed by springs against the trolley-wires. The current passes down these through switches to controllers at each end of the car, one set being used at a time.
Fig. 238.
