Series circuits are most often used for lighting. The most familiar example is a string of classic Christmas tree lights, in which the loss of one bulb shuts off the flow of electricity to each bulb further down the line. However, series circuits can be used for any situation in which a single cable is used to supply power to a number of widely spaced lights or other devices.
A series circuit uses a single cable with multiple resistors on it, explains Electrical Construction & Maintenance. Other models, such as parallel circuits, split a single line into several and put a resistor on each. The series circuit must handle larger voltages than parallel circuits, so it requires a more expensive and heavily insulated cable. However, it only requires the single cable. This allows applications, such as runway lighting, which must stretch as far as two miles, to be made much more cheaply, with a single power source and only a single cable. Modern models also include bypasses so the loss of one resistor does not break the circuit.
A series circuit must be able to cope with the sum of all resistances on the circuit. Thus, the voltage must be high enough to compensate for the voltage drop from each resistor.