![]() While shunts serve to remedy an open circuit, fuses work to prevent damage due to a short circuit or any other dramatic increase in current. I must have caused some sort of short circuit when I jolted the wire. I unplugged, replugged … unplugged, replugged the string. The string of lights remained plugged in so I was stymied as to what happened. Recently, as I was putting up lights, I tripped on a wire and the lights went out. Now the shunt has gone from an insulator to a conductor, and current passes along shunt, keeping the circuit closed, and the remaining lights burning. If the filament burns out, however, the high temperature from the burnout will cause the substance coating the shunt to melt off, revealing the lower resistance wire beneath. In other words, electricity cannot pass across the shunt as long as the filament exists, because the coating gives the shunt a higher resistance initially than the filament, and the electrical current avoids the shunt in order to find the path of least resistance through the filament. Initially, they are coated with a substance that makes them an insulator. In incandescent holiday lights, shunts are small wires wrapped beneath the filament. If multiple bulbs were blown out, this would become exceedingly difficult.Įnter the "shunt." What is a shunt, you ask? I will tell you! Shunts and Fuses Save the DayĪ shunt is any device that allows current to continue flowing through a circuit by creating a path of lower resistance than the original path. If this were the case, you would have to check each bulb individually to see which one was blown out. When additional strings of lights are attached to the end of a string, these lights are added in parallel to the original strand.īut what about when a bulb goes out in a series? It used to be that when one bulb went out, the entire series would go out. This is why sometimes only one portion of your lights will become defective, while others will remain functional. This way, when one series of bulbs becomes defective - say, from a loose bulb - it should have no effect on any of the other series of bulbs, since they are in parallel to the defective series. If the current is too great, the filament will melt, or blow out, causing the circuit to become open. ![]() If the circuit is broken, or open, no electricity will pass over the filament and it will not light. The more current that passes over a filament, the hotter it will get, the brighter it will burn, and the quicker it will burn out. In a simple circuit, including one in an incandescent light bulb, electricity travels through a closed circuit, passing over a filament, causing it to glow brightly. Holiday lights are a great way to learn about the flow of electric current. While stringing up lights, I wanted to learn how exactly holiday lights work. Our stockings are hung by the chimney with care and we have strings of lights decorating our cubicles. We're getting into the holiday spirit here at the Department of Energy. We recommend reading the entire post, because LEDs and incandescent lights have a lot in common.Īny questions that we didn’t answer here? Tweet at us ( and let us know. Since more consumers are switching from traditional incandescent bulbs to energy efficient LED bulbs - particularly around the holidays - we’ve updated our popular holiday light explainer with a section to help you understand LED holiday string lights (and how to fix them). This is good news, and you don't need to do anything further, other than taking care not to plug in multiple high-voltage electrical items simultaneously in the same area of the house.Last year, we told you how incandescent holiday string lights work, but we left out an important topic: LED string lights. If the bulbs light back up, an overloaded and tripped electrical circuit was likely your problem. You can often tell which circuit was tripped because the switch will be slightly out of alignment with the others. Once you locate the circuit you believe is tripped in the panel, move the switch all the way to the "off" position, and then to the "on" position. ![]() To do this, locate the labeled circuit in the metal circuit box panel, which is usually found in your home's utility room, basement, or garage. To check the circuit breaker, plug the lights into an electrical outlet. An overloaded electrical circuit - a situation where more electrical demand is placed on an outlet than it can handle - is the most common (and least serious) reason for this, he explains. If none of the bulbs in a string of Christmas lights work, and you also notice that other lights in the same section of the house go out, you've likely tripped the circuit breaker, says Bello. When to try it: When none of the lights work. ![]() Reset the circuit by turning the switch off and on again. ![]()
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