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

CONCEPT:

Eddy current- Eddy current is defined as the induced electromotive force produced in the coil when there is a change of magnetic flux linked to the given coil or we can say that the eddy current is the loops of electrical current induced within the conductors by changing magnetic field in the conductor. It is called as eddy current.

EXPLANATION:

1. Induction furnace- An induction furnace, it is having a coil that is carrying an alternating current that surrounds the chamber of the metal. In this furnace, the eddy currents are induced in the metal and the circulation of these currents will be producing extremely high temperatures which make metal melt.
2. Magnetic braking in trains - In trains, the eddy current is used in the brakes. It is used to slow or stop a moving object by dissipating its kinetic energy.
3. Electromagnet- Electromagnetic is the substance in which a magnetic field is produced by supplying the electric current through the material. When the electric current is supplying through the material, there is a change of magnetic flux into the material which produces loops.
4. Electric heater- The electric heater works on the principle of Joule's heating effect. It states that the heat produced in the resistor is directly proportional to the resistance for a given current and the time in which current is flowing through the conductor.

​Hence, option 4) is the correct answer.