Looking at the schematic diagram, we see that points 1, 2, 3, and 4 are all electrically common. So are points 8, 7, 6, and 5. Note that all resistors as well as the battery are connected between these two sets of points. We can have circuits that are a combination of series and parallel, too:. In this circuit, we have two loops for electrons to flow through: one from 6 to 5 to 2 to 1 and back to 6 again, and another from 6 to 5 to 4 to 3 to 2 to 1 and back to 6 again.
Notice how both current paths go through R 1 from point 2 to point 1. This is just a preview of things to come. In a purely parallel circuit, there are never more than two sets of electrically common points, no matter how many components are connected. Components can be connected in series, parallel, or in a combination that is sometimes referred to as series-parallel. The first step to understanding electric circuits is being able to recognize when components are in series, parallel, or a combination, as well as the effect these configurations have on the circuit itself.
One of the most important things to remember is that every component behaves differently when arranged in series versus parallel. There are rules for solving series circuits , as well as rules for solving parallel circuits. Throughout this course, we will see examples of how to solve problems that are increasing in complexity and learn how to understand and use some of the most important types of circuits. A series circuit is formed when components are connected via a single conductive path with each other.
In the circuit diagram below, two components called resistors R 1 and R 2 are connected in series with each other to complete the circuit.
Resistors are simply components that provide a defined amount of electrical resistance to any current that passes through them. We can see that R 1 and R 2 are connected to form a single conductive path.
Electric current flows from the positive terminal of the battery, through R 1 and R 2 , to the negative terminal of the battery. The current through all components is the same. A circuit that is made of components connected in parallel is called a parallel circuit.
Components are connected in parallel if they are connected by multiple conductive paths. On the left side of the circuit, we can see a three cell battery supplying 1.
Some of the current goes down through R 1 , a 5 Ohm resistor. Some of the current does not go through R1 but instead goes through R 2 , a 10 Ohm resistor. In other words, current flows through both R 1 and R 2 simultaneously. The current then continues to travel toward the negative terminal of the battery.
Yet the current is different in each path. Current always follows the path of least resistance. The higher the resistance, the less current will flow through a certain path. In the above circuit, R1 has a resistance value of 5 Ohms, whereas R2 offers a resistance of 10 Ohms. Since R 1 has half the resistance of R 2 , the current through R 1 will be twice the current through R 2.
However, the voltage is the same for each path in this circuit. The conductors on the positive side of the battery are all connected, as are the conductors on the negative side. So the voltage difference between the two sides is just the voltage of the battery, which is 1. It is common to find circuits that have both series and parallel components.
These are called series-parallel circuits. For example, the circuit below shows resistors in both series and parallel, forming an interesting series-parallel circuit.
In a series circuit, if a lamp breaks or a component is disconnected, the circuit is broken and all the components stop working.
Series circuits are useful if you want a warning that one of the components in the circuit has failed. They also use less wiring than parallel circuits. In parallel circuits different components are connected on different branches of the wire.
If you follow the circuit diagram from one side of the cell to the other, you can only pass through all the different components if you follow all the branches. In a parallel circuit, if a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working.
And, unlike a series circuit, the lamps stay bright if you add more lamps in parallel. Parallel circuits are useful if you want components to continue to work, even if one component has failed.
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