Powering Slot Cars
Each car has a negative and a positive metal contact on the motor which make contact with corresponding metal contacts or rails built into the track. A wired controller or an infrared receiver for wireless controllers plugs into the track. Using a trigger on the controller the driver sends electrical current to the track powering the slot car motor.
Controlling Slot Cars
Remote control vehicles that are not slot cars generally have forward and reverse controls. They typically make turns by going in reverse until the rear wheels lock in place forcing the vehicle to turn left or right. With slot cars there is only forward movement.
How much the driver pulls back on the trigger throttle of the controller determines how fast the slot car races around the track. In placing the slot car on the track you have to be sure to place it facing the right direction. If you put the car on the wrong way the car will go in reverse and spin backwards out of control. Although this doesn't hurt the slot car any it can lead to a pile up at the starting line and that would make a lot of drivers very unhappy. So be sure what direction you are supposed to follow when placing your slot cars on the track.
Slot Car Size
Slot cars are scale size models of full-size cars. 1:24 (7"-8" long) and 1:32 (5"-6" long) scale are common racing sizes. The smallest slot cars are HO scale of about 2"-2.5" long. Learn more: What Scale of Slot Car is Best?

