The Joule's Law Demonstrator is an experimental instrument designed specifically for high school and university physics classrooms, used to visually demonstrate the relationship between the thermal effect of current and the magnitude, resistance, and duration of current (Q=I ² Rt). By visualizing changes in temperature or liquid column height, students can quantitatively verify Joule's law within a few minutes and develop their experimental exploration skills. Application scenario: Group experiment of "Thermal Effect of Current" in junior high school; Exploration Experiment on Constant Current in High School; Physics Teaching Methodology Course in Normal Universities; Interactive display at science popularization venues.