Why Bulbs Get Dimmer in Series Circuits

Next Generation Science

In this engaging science demonstration from the Lighthouse Lab, the presenter explores the physics of electrical circuits, specifically focusing on how adding components impacts circuit performance. Building on previous knowledge about adding batteries, this video investigates the inverse effect: what happens when electrical loads (light bulbs) are added to a series circuit. The video provides a clear, step-by-step experiment that allows students to visually verify the relationship between load and brightness. The content covers key physics concepts including series circuits, voltage, and electrical load. Through a practical demonstration using standard classroom circuit kits (batteries, wires, clips, and bulbs), the video illustrates how energy is distributed in a closed loop. The central theme explains the concept of "voltage sharing," demonstrating that a fixed amount of voltage must be split between components, resulting in reduced energy available for each individual bulb. This video is an excellent resource for upper elementary and middle school science classrooms introducing electricity. It serves as a perfect anchor for prediction-based learning—allowing teachers to pause before the switch is thrown so students can hypothesize the outcome. The clear visual evidence helps dispel common misconceptions about electricity consumption (e.g., that the first bulb uses up the power before it reaches the second) by showing that both bulbs dim equally.