A magnetic brake is an apparatus that uses intense magnetic forces to slow down a vehicle. There are many different kinds of magnetic braking systems, including those that employ magnetic repulsion to create resistance and those that use electromagnets to activate conventional friction pads. These are on a range of vehicles, including trains and roller coasters. The most popular kind of magnetic brake is an electromagnetic brake, which uses magnets linked to a set of brake pads to conduct an electric current. The magnets grip the brakes over a brake disk as they are drawn to one another, creating friction to give stopping power. There are several variants on this kind, such as so-called failsafe brakes that use extremely powerful permanent magnets that are by nature attracted. In a power outage or other emergency, they instantly engage since they can only be kept apart by an opposing magnetic actively working to keep them apart.