Jargon buster
Voltage
Voltage is the ‘pressure’ at which the electricity is forced along the wires and through the track. The plug sockets in your house are 240 volts, but your model railway can only run on 12 volts. Your controller or controller hub has something inside it called a transformer, and this converts the 240 volts down to 12 volts so it’s safe to use. The reason that the electricity comes into your house at such a high voltage is that it is more efficient to move across the country at higher voltages.
Current
Current is the rate at which electricity flows along a wire. It’s measured in amps. The current changes depending on the diameter of the wire through which the electricity is flowing. For example, you might have the same voltage in two separate wires, but if one wire is thicker than the other then more electricity can flow through a set point in a set time frame, so the current will be much higher. This is something to bear in mind when wiring your layout as you may need thicker wires to deliver the required current around the whole of the track. Be aware that the thinner the wire is, the higher the level of resistance will be. A higher level of resistance creates more heat, which is not a good thing around wooden baseboards.
Analogue layouts
On analogue layouts, the current on the track directly affects the locomotives because as the current increases so will the speed of your locomotives. The dial on analogue controllers lets you change the voltage to allow more (or less) current through. Some analogue models have difficulty moving at reduced speeds as there isn’t enough current to keep them moving.
Digital layouts
Because the controller does not control electricity flow on digital layouts, you’ll need to make sure that a sufficient current is constantly supplied to the track to move the locomotives.