Magnetic brakes are used to slow or completely stop a moving object or vehicle. A great example of this are eddy current brakes. This type of brake uses electromagnetic force as its drag force to slow or stop the moving object. It is commonly used in high speed trains or in roller coasters. This force is generated when a magnet is dragged along a conductive object (that is in a fixed position) and induced with eddy currents through electromagnetic induction.
You can actually replicate this in two ways.
What you will need:
- Neodymium magnet
- Wooden molding
- Aluminum angle
- PVC tube (diameter should be bigger than the magnet)
- Aluminum tube (diameter should be bigger than the magnet)
What you need to do:
- Combine the piece of wooden molding and the aluminum angle. Make sure that the transition edge between the wooden piece and the aluminum is flat to keep the path of the magnet straight.
- Hold the wooden end at a 90 degree angle and allow the neodymium magnet to slide from the wooden surface to the aluminum surface.
- Observe how the magnet is rapidly sliding over the wooden surface and slows down as it goes through the aluminum angle.
- Take the PVC tube and let the neodymium magnet slide inside. Observe how fast it reaches the bottom of the tube.
- Take the aluminum tube and drop the magnet inside to let it slide. Observe how long it takes to reach the bottom and compare it with the time it took the magnet to slide down the PVC tube.
What just happened:
When the magnet is sliding down an aluminum surface, it is much slower compared to the speed of the magnet as it slides down the wooden or PVC surface. As the magnet is traversing the wooden or PVC surface, it is attracted to the aluminum surface – that and the gravitational pull makes it travel faster. But when it reaches the aluminum surface, the metal goes through a change in magnetic field that induces electric current in the metal. These currents are known as eddy currents. The generated current has its own magnetic field that exerts a force on the magnet as it slides down. This causes the slower motion of the magnet.
