How does energy transfer from one coil to another without any direct electrical connection between them? This is the essence of the transformer concept. On this page we explain the working principle step by step, exactly as a student needs it for an exam and an engineer needs it for an interview.
How the Transformer Works, Step by Step
- The primary winding is fed with an alternating voltage, causing an alternating current to flow through it.
- This current produces a changing magnetic flux that flows through the iron core.
- The changing flux links the turns of the secondary winding, inducing a voltage in it (Faraday's law).
- When a load is connected to the secondary, a current flows and power is transferred from the source to the load.
Induction, Not Conduction
In a healthy transformer there is no direct electrical contact between the primary and secondary; energy transfers solely through mutual induction. This point is fundamental: insulation between the two windings is a safety and operational requirement, and any contact between them is considered a serious fault.
The Role of the Iron Core
The core, made of high-permeability silicon steel, provides an easy path for the magnetic flux between the two windings, increasing the magnetic coupling and reducing leakage. Read more details on the function of the iron core page.
Imagine the primary winding continuously "shaking" the magnetic field in the core, while the secondary winding "picks up" this vibration and converts it into a voltage. When the vibration stops (a steady direct current), the pickup stops too.
Sample answer: The transformer works by mutual electromagnetic induction: an alternating current in the primary winding produces a changing magnetic flux that flows through the iron core, linking the turns of the secondary winding and inducing a voltage in it proportional to the turns ratio, without any direct electrical connection between the two windings.
A common interview mistake is saying that electricity "passes" from the primary to the secondary through the wires. In reality, energy transfers magnetically through the core, and the two windings are completely electrically isolated from each other.
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