Animated Solution for Physics - Electromagnetic Induction: The core of any transformer is laminated so as to

Eddy Currents

Imagine you are designing a transformer. You have your primary coil, your secondary coil, and a solid iron core to perfectly guide the magnetic flux from one to the other. It seems like a flawless setup. But when you turn it on, the core gets incredibly hot, and you are losing a massive amount of energy. What went wrong?

The culprit is a phenomenon known as Eddy Currents. According to Faraday's Law of Induction, whenever a conductor is subjected to a changing magnetic field, an electromotive force (EMF) is induced in it. In a transformer, the alternating current in the primary coil creates a continuously changing magnetic flux. This flux doesn't just pass through the secondary coil; it also passes right through the iron core itself!

Since iron is a conductor, this changing flux induces an EMF within the bulk of the core. This EMF drives circulating currents—like swirling eddies in a river—right inside the metal.

Why are these eddy currents a problem? Because every conductor has some resistance, $R$. When a current $I$ flows through a resistance, energy is dissipated as heat according to Joule's Law:

If the core is a single, solid block of iron, it provides a very large cross-sectional area for these currents to flow. A large area means a very low resistance. Consequently, the induced eddy currents become massive. Since the power loss depends on the square of the current, a solid core leads to catastrophic energy losses and dangerous overheating.

How do we defeat these swirling currents without losing the magnetic properties of the iron core? The solution is brilliantly simple: Lamination.

Instead of using one solid block, we slice the core into many thin sheets (laminations). Crucially, we coat each sheet with a thin layer of insulating varnish before pressing them back together.

By doing this, we are effectively placing roadblocks in the path of the eddy currents. The currents can no longer circulate through the entire bulk of the core; they are confined to the narrow thickness of each individual sheet. This drastically reduces the cross-sectional area available for the current, which in turn significantly increases the electrical resistance $R$ of the path.

With a much higher resistance, the magnitude of the eddy currents $I$ drops sharply. And because the power loss is proportional to $I^2$, even a small reduction in current leads to a massive reduction in wasted heat.

Therefore, the core of any transformer is laminated specifically to reduce the energy loss due to eddy currents.