Christmas lights are a perfect example which physics is wildly incorporated in. The lights that are wrapped around Christmas trees and houses use power and energy and are measured in watts. They are circuits which means that current flows within them to keep them lit up. These Christmas light circuits begin working when one end is being plugged into an outlet to begin the flow of energy. But the cool thing about these lights is that if one bulb goes out, the rest of the string is able to remain lit. Most Christmas lights are made of incandescent bulbs connected to an electric circuit. When electric current is going through the circuit, it becomes hotter, which creates the light and is ultimately the reason for why bulbs eventually burn out!