Question

Eddy current can be minimised by
(A) Using a laminated iron core
(B) Moving the conductor rapidly
(C) Moving the conductor slowly
(D) Using a metallic core

Answer 1

Hint: In general, to minimize current, one should increase the resistance. Laminations are made of materials which are insulators. Hence laminating a core can reduce the currents.

Complete step by step answer
In a transformer, a changing current (usually alternating current) is allowed to flow through a coil of wire wound around a magnetic material (like iron). This alternating current causes a changing magnetic field to be induced within the encompassed area of the coil (as in a solenoid). Furthermore due to the presence of the magnetic material, the magnetic field lines are directed through and around it. These magnetic fields are made in the form of a hollow square but with thickness and height. The coils are wound around one of the sides of this square magnetic material, so when the magnetic field due to the current flowing through the coil is created, it is generated within the material, which allows the electric field to circulate through its entire perimeter. Then a coil is wound on the opposite side of the square, this changing magnetic field induces a changing current in the other coil.
However, since magnetic materials are also conductive material, current is also induced within itself, called eddy. This current generates heat and causes loss of energy in the transformer. To reduce the eddy current we can laminate the core to increase the overall resistance of the magnetic material.

Hence, the correct option is A.

Note
In actuality, loss of energy through heat is not the only form of energy loss due to eddy current. When eddy current is generated, the changing current also generates its own magnetic field which opposes the magnetic field generated by the primary coil. Hence, it reduces the overall magnetic field.