The Christmas lights on this tree may have cost $5 or $25, depending on how the circuit is constructed. If all of these lights are on a single straight line (series) circuit, and if the filament in one of the bulbs burns out, then all the lights will go out and you will not know which light bulb burned out. In order to fix the problem, you must go through the string of lights and replace each bulb one-at-a-time in order to determine which bulb was burned out. The only advantage to such a string of lights is that they are inexpensive. Another way of designing this string of Christmas lights would be to put each light on its own individual circuit (parallel). With that design, if one of the bulbs burned out, only that light would go out and it would be obvious which light bulb needed to be replaced. Of course, a string of Christmas lights designed and built in that way would be much more expensive.
In this unit, we will examine and learn the mathematics involved in both series and parallel circuits and also circuits that are a combination of series and parallel construction.
Series circuits are simple and comparatively inexpensive to design, but require every resistor (device) in the circuit to be functional in order for the rest to work. Parallel circuits may be more complex and expensive, but have some advantages that may be worth the cost. There are appropriate applications for both types of circuits and both are common. More common than either individual type of circuit is a combination of both that may offer capabilities and advantages that neither individual type of circuit can provide.
Ammeters and voltmeters are tools used to evaluate the flow of current through a circuit and must be connected to the circuit appropriately in order to measure the flow without significantly changing it.