 
A common sight in amusement parks and at street fairs are the bumper cars. These are unusual vehicles, in that the driver gets a lot of control ... he can move the car forwards, left or right, and turn a complete circle in place. The indoor nature of this attraction requires that the vehicles have electric motors, but batteries would make them too heavy, and cords would get hopelessly tangled. How do the cars get their electric power? The answer can be seen if you look closely at the roof of the building the cars are in. Bumper cars are always in a building, because the power comes through the roof. Have a look at the picture below ... 
The ceiling is covered with a rectangular grid of wires, which carry an electrical current. A bumper car has a tall pole behind it that touches the roof, and makes contact with this electricity.The entire car is like a 'short circuit' ... some of the electricity from the ceiling circuit escapes to the floor, which is 'grounded', or connected to the earth. Along the way, this escaping electricity has to pass through the electric motor in the car, and this makes it run. Although the floor forms part of the path that the electricity uses to escape to the earth, it is safe to walk on, since it is a better conductor than you are. Electricity passing from the cars can more easily escape into the earth through the floor than you, so it does. |