Why is the iron core of a transformer laminated?
To decrease eddy currents, transformers have their iron cores laminated. Eddy currents are small currents caused by the fluctuating magnetic field generated by the alternating current in the first coil.
They must be kept to a minimum in order to prevent interference with the flow of electricity from the primary coil to the secondary coil.
The core is not intended to carry current. It serves as a conducting loop which undergoes a changing magnetic field, therefore small current will be induced in it. These are known as eddy currents.
The core is laminated to minimize these currents, which interferes with the effective transfer of energy from primary to secondary coils.