We know that a closed circuit contains three requirements: a path, a power source, and at least one resistor. The behavior of the current that flows through that circuit obeys Ohm's Law, which states that the voltage through a circuit will equal the product of the current times the resistance of the circuit.

So far we have looked at circuits with only one resistor, but these types of really simple circuits don't really occur that often in the real-world. More than likely you have encountered circuits that contain more than one resistor. Remember, resistors can take many forms—a fan, a light bulb, or a toaster—just to name a few. What happens to the current when you connect more than one light bulb in a circuit? Will it still obey Ohm's Law?

In this lesson, you will study one way that resistors can be connected to one another in a circuit: in series. A series circuit contains more than one resistor that is connected in a circuit so that there is only one path through which the current flows.