Transcription: In this circuit, the light bulbs are said to be hooked in series because electricity must pass through the first light bulb to get to the second one. As long as both light bulbs continue to work, this system works fine and electricity flows. However, if one of these light bulbs were to burn out, electricity would not be able to pass through it. As a result, there would no longer be a complete circuit and both light bulbs would go out even though only one of them was bad.