No matter what kind of train you buy, electricity will run it. You may have chosen a choochooing, smoke-puffing steam engine or a growling diesel. It makes no difference, for a tiny electric motor working through a worm-drive makes the wheels go round. The motor pushes an extra piston on your steam loco, puffing out smoke which is really vaporized oil, and making the lifelike sounds of the engine.
Electricity lights the headlight, blows the whistle, actuates the switch that sends your train into reverse. It throws your remote-control switches, works the uncoupler, causes the racing baggage car to pick up the mailbag on a stanchion without slowing down. Electricity operates your unloading cars, your talking station, and trackside loading devices. Since it does so many things, perhaps we should learn a little more about this versatile and powerful tool.
To perform work, electric current must flow. It cannot just travel up to a lamp bulb or motor and stop there. It must pass through the device, causing it to function as intended, and return to where it started. With direct current, the electricity is positive on its way to the device to be operated, negative on its return.
The positive terminal is comparable to the north pole of a magnet, the negative to the south pole. The flow of electric current may be likened to the flow of blood in your body, which moves from the heart through arteries carrying oxygen and other essentials, reaches its destination and passes through it to deliver the needed materials, then returns to the heart by way of the veins. In the process it has performed some very useful work.
How does electricity perform the work it does? In various ways, one of the most common being through resistance set up to it. To use a familiar example, if water is flowing over a dam and has nothing to impede its fall, there is no resistance. If you put a water wheel or turbine in the stream of water, the wheel offers some resistance to the flow. But the water pushes the paddles on the wheel out of the way and keeps flowing, thereby turning the water wheel and accomplishing work.
This is essentially what happens when a lamp bulb is lit. Electric current flows along copper wires, which offer very little resistance. Inside the light bulb it flows into fine filaments offering great resistance. The current flows in spite of this resistance but does some work in the process, by heating and making bright the filament.
What if the wire from the positive terminal should touch the wire from the negative terminal before it reached the bulb? The current would flow from one wire to the other as if the dam had been broken.
The rate of flow, or amperage, would suddenly increase so much that if the current was coming from a battery it would drain it completely in a very short while. If the current was coming from an electric inlet in your home, it would flow so rapidly that it would heat up another resisting device, known as a fuse, in your fuse box.
The fuse would burn up, or melt, so the current could not flow through it. This is a short circuit, and occurs whenever current is allowed to flow from one wire to the other without any resistance between them. If you didn't have a fuse to break off the flow of current at such times, so much heat might be generated that a fire would start.
You should enjoy your model railroad a whole lot more, now you know what makes the wheels go round! |
