Originally Answered: What is the function of the tiny cylinder attached to a laptop charger cable? It is a ferrite bead, used to suppress high frequency electromagnetic noise from your charger from reaching the AC mains.Click to see full answer. Regarding this, why laptop charger has a small cylinder?The ferrite bead is used to prevent electromagnetic interference (EMI) to a device or from a device. The cylinder also reduces radio frequency interference (RFI). The reason behind preventing the signals is to stop them from interfering with other electronic devices nearby.Subsequently, question is, what is the box on my laptop power cord for? That box does three main things: It reduces the voltage down to something the laptop can manage. It converts the AC power coming out of your wall to the DC power your laptop needs to run. Smooths out power fluctuations from the wall to make sure the power your computer receives is a constant, steady voltage. Then, why do some USB cables have a cylinder? The cylinders are designed to reduce the possibility of electrical interference with other electrical sources and devices. The cylinder is called a ferrite bead, ferrite core, or, more generally, a choke. Cables can act like unintentional antennas, broadcasting electrical interference (“noise”) or picking it up.What is the black cylinder at the end of laptop charger? Ferrite bead