Magnetic Braking (Eddy current brake)

Unlike mechanical brakes, which are based on friction and kinetic energy, magnetic braking is a frictionless type of braking system that rely on electromagnetism to stop objects from moving.

When a conductor passes through a magnetic field, a type of electric current is created, called Eddy currents, which in turn creates an opposing force that spins inside the conductor. This creates a magnetic field that acts in the opposite direction of the external magnetic field. The opposing magnetic field will decelerate the motion of the conductor that passes through the external magnetic field and eventually bringing it to a stop.

Continuous generation of Eddy currents in the conductor will generate heat, which is used in many applications in biology and medicine. One such application is diathermy, where the heat generated by Eddy currents relaxes muscles and joints, reduces inflammation and swelling, and improves blood circulation.

Here, a magnetic weight will be tied to a fulcrum and allowed to swing freely. By putting a piece of conductor (copper plate) along the pendulum’s path of motion, Eddy currents will be generated which produces an opposing electromagnetic field that will stop the movement of the pendulum.

A copper disc is suspended through the central bore. A magnetic field is then created by placing two magnets of opposite poles in proximity (approximately 1 cm apart). Visitors will then spin the copper disc (the “wheel”) and while the wheel is still spinning, the magnetic field is then placed over the wheel. The wheel will decelerate quickly and eventually comes to a halt.

Because aluminum is a non-ferrous conductor which acts similarly as copper, this activity can be easily replicated at home by using fridge magnets and aluminum cut-outs from soda cans.