Question

Why is the iron core of a transformer laminated (thin sheet) instead of being in one solid piece?
A. To increase the energy losses due to eddy current
B. To reduce the energy losses due to eddy current
C. No reason
D. none of the above

Answer 1

Hint: The basic working principle of a transformer is the generation of induced electromotive force in the circuit. When current through primary windings vary, they induce current in the secondary winding. This process results in the formation of eddy current in the transformer circuit. We will study the core of a transformer and the nature of eddy currents to know the reason why the core of a transformer is laminated in a thin sheet.

Complete step-by-step answer:
A transformer is basically a passive electrical device which has the capability to transfer electrical energy from one electrical circuit to another or multiple electric circuits. A varying electric current in any one coil of the transformer produces a varying magnetic flux in the core of the transformer, which then induces a varying electromotive force across any other coil wound around the same core. Electrical energy can be transferred between separate coils without a metallic, or conductive, connection between the two circuits.
This magnetic circuit, which is more commonly known as the transformer’s core is designed in a way to provide a path for the magnetic field to flow around, which is necessary for the induction of the voltage between the two core windings.

The iron core of a transformer is made of laminated silicon steel with special insulated coating to limit Eddy current loss in the transformer. Electrical steel, also called lamination steel is specialty steel tailored, or designed in a way to produce specific magnetic properties, such as a small hysteresis area, called as low core loss or small energy dissipation per cycle, and high permeability.
An eddy current is a type of swirling current, rotating current developed in a coil, set up in a conductor in response to a varying magnetic field. By Lenz's law, the current swirls in such a way so as to create a magnetic field opposing the change in the external magnetic field. To do this in a conductor, electrons swirl, or rotate, in a plane perpendicular to the plane of magnetic field. As eddy currents have the tendency to oppose, they cause energy to be lost. Eddy currents generally transform more useful forms of energy, such as kinetic energy, into heat energy, which is actually much less useful.
The iron core of a transformer is laminated with the thin sheet; the laminated iron core prevents the formation of eddy currents across the core and thus reduces the loss of energy.

So, the correct answer is “Option B”.

Note: Students should note that the core of a transformer has the function to provide an easy path for the magnetic field to flow around in the circuit. For this purpose, the core is designed in a way to pass maximum current in the secondary winding of the transformer to receive the maximum output.