Understanding Electricity – The Bare Essentials

You don’t need to be an electrical engineer to wire a model railroad. But a basic understanding of electricity, in particular Alternating Current, will make the rest of these tutorials much easier to follow. If you want to learn more about electricity, there are lots of great sites for all knowledge levels online already. Our aim here is simply to give you some added perspective on how your trains really work.


Nearly all O Gauge trains use Alternating Current (AC) electricity to operate. Direct Current (DC) is far more common in two-rail trains. All of the tutorials on this site will be based on AC. Let’s get DC out of the way quickly.

AC-DC cuves

Graphic depiction of DC and AC 14V waves.

Direct Current is a very simple form of electricity. It can be found in static and lightning. Once created, it is stored, as in a battery, until a circuit is completed. With the circuit complete, the electricity flows in one direction. Most DC uses are low voltage – 12 volts or less. To produce work, a positive and negative charge must be present.

Alternating Current is a little more complex. AC switches back and forth between a positive and negative charge across the zero plane. On a graph, this is shown as a sine curve.  Work is accomplished by connecting the charged or “hot” AC to a ground. AC is the same type of electricity found in your house – we just use a lower voltage on our layouts. In the United States, all AC current alternates between + and – at a rate of 60 times / second (60 Hz). Overseas, the rate is only 50 Hz. All of Lionel’s trains are designed to run off of 60 Hz frequency. Adaptors can however be found to adapt our transformers to other electrical systems like other small appliances and electrical devices.

Variable Vs. Fixed Voltage

With a variable voltage control, the amount of voltage can be adjusted. This is what allows a model  train to speed up and slow down. As your AC voltage increases, the peaks and troughs of the curve get taller. Fixed voltage remains at a constant level. This is more desirable for lights and other accessories that have only one intensity or speed of operation. For more understanding of why you should have both on your layout, see this video: [youtube=http://www.youtube.com/watch?v=ghWxxO5h3JI&feature=g-upl]

Amps, Volts and Watts

If you’re new to the hobby, or quite possibly even if you’ve been running trains for years, the difference between amperage, voltage and wattage may be a mystery – or maybe you didn’t even know there was a difference. Amps, Volts and Watts actually refer to three very different but related electrical properties. Here’s what you need to remember:

  • Amperage (Amps) = the AMOUNT of power available
  • Voltage (Volts) = the FORCE of the power
  • Wattage (Watts) = the WORK that the power can do

The three are tied together like this: Watts = Amps x Volts (W=A*V). Conversely, Amps = Watts / Volts and Volts = Watts / Amps.  With this simple equation, you can figure out the third property of a transformer for example if you only know the first two. This can be very helpful when deciding what type or how many transformers you may need to run your layout as it grows. For example, if a transformer is advertised as having “180 Watts” of power, and you know that its maximum voltage is 18, then 180 Watts / 18 Volts = 10 Amps.

You don’t need to be a master electrician to build a model railroad, but knowing the basics will make it much easier to understand how your trains work – or more importantly why they might not be! If you’d like another review of all of this, see our instructional video: [youtube=http://www.youtube.com/watch?v=rAnIJRnRC4g&feature=g-upl]

5 thoughts on “Understanding Electricity – The Bare Essentials

  1. I don’t understand Billy Ray’s anticipation of connecting two transformers to one track. FIRST- does he mean one LARGE ovals with sidings, but isolated?
    Or is this one track really a layout of two (or more) isolated continuous loops of track CONNECTED by switches for flexible trainS travelling at the same time AND, possibly, on the same line (not necessarily one near the other.)
    My concern has ALWAYS been power to the outreaches of the 10’x20′ table on which I am currently laying track.
    Finally, these ovals which will intersect MUST CONNECT. How do I provide power to the loops? I do not want to take the coward’s way out and have five lines that merely cross each other.

    • Mike,
      In your case, you’ll want to see our pages on Bus Wires and Blocks. The former will help you get power to the outreaches of your layout. The latter will allow you to connect as many loops, sidings, etc. as you’d like and control trains independently.

  2. I have a 1936 standard gauge train and 1955 N gauge train……can I run both trains simultaneously off a 275 watt transformer

  3. I believe I have a standard gauge 1930 era Lionel model train. Outside rails are about 2″ apart. The original power supply was toast. I thought I found a source source stating that it used a 0 to 18 volt dc supply. Apparently that’s wrong? Do you know of a good source for a power supply?

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