Parallel circuits differ from series circuits in two major ways. Parallel circuits have more pathways in their circuit system, and parts of a parallel circuit are aligned differently than they are in a series circuit; this alignment affects the amount of current that flows through the circuit.
Basic Circuit Structure
Simple circuits consist of a power source, such as a battery, and a conductor, such as copper or silver wire. Each end of the conductor is connected to one of the battery terminals. When the circuit is active, electrons flow freely through the circuit.
For most electrical systems, it's important to control the current flow. Scientists use natural materials, called resistors, to slow down the flow of the current. How much current flows through the electrical system depends on the placement of these resistors, which is different for the two circuits.
In series circuits, resistors are connected together in a line between the two ends of the power source. Current flows through each resistor, one after another, because it has no other paths to follow. Each resistor reduces the amount of current as it passes through the circuit so the measurable current of the circuit is much less than a circuit having a single resistor.
These circuits look like multilaned highways, having several pathways lined up parallel to each other. Each pathway has its own resistor. As current flows through this circuit, the current splits, sending some of the current through each of the pathways. Although the resistors control the flow of current through each pathway, the circuit has more current than a single-pathway, single-resistor system.