Analyze: In the series circuit what characteristic was common throughout the experiment? What changed as you added more light bulbs?

In the series circuit, the most common characteristic throughout the experiment is that the electric current has a single path to flow and if one part fails, the whole circuit will not function.

In addition, the current is equals to voltage supply over the total resistance of the circuit and if you added more light bulb in the series, the current will decrease and the brightness of each bulb will decrease.