In which of the following devices, the eddy current effect is not...

In an Induction furnace, a coil carrying AC surrounds the chamber of metal. Eddy currents are induced in the metal. The circulation of these currents generates high temperature which is used to melt metals. After melting, these melted metals are mixed to make alloys of the same composition.

Mechanical brakes are based on friction. But, magnetic brakes have Eddy current. Brakes have a disc which rotates perpendicular to the magnetic field. As the disc rotates, Eddy currents are induced. Then power is dissipated throughout the disc which produces a braking torque.

Eddy current effect is used in the electromagnets are widely used. An example of this can be the ordinary electricity meter in every house. Eddy currents make the aluminium disk in an electricity meter to spin. Then this number of spins or revolutions shows the usage of electricity.

Electric heaters produce heat. They take all the energy and supply it in the form of heat. Eddy current has an efficiency of 100% which means it gives all the energy to do the work. So much heat cannot be used in electric heaters.

Hence, Eddy current is not used in an electric heater.