Physics – 4.5.6 The transformer | e-Consult

A simple iron-cored transformer operates on the principle of electromagnetic induction. It uses two or more coils of wire, called coils, that are electrically isolated but magnetically linked. The core is typically made of iron, which enhances the magnetic flux.

The transformer consists of a primary coil and a secondary coil. An alternating current (AC) is supplied to the primary coil. This alternating current creates a time-varying magnetic field in the iron core.

This changing magnetic field then induces an electromotive force (EMF) in the secondary coil. According to Faraday's Law of Electromagnetic Induction, the magnitude of the induced EMF is proportional to the rate of change of the magnetic flux and the number of turns in the coil. The ratio of the number of turns in the primary coil (Np) to the number of turns in the secondary coil (Ns) determines the voltage transformation ratio.

Voltage Transformation Ratio:

• Step-up Transformer: If Ns > Np, the secondary coil has more turns than the primary coil. The voltage in the secondary coil is higher than the voltage in the primary coil. This is used to increase voltage for long-distance transmission.
• Step-down Transformer: If Ns < Np, the secondary coil has fewer turns than the primary coil. The voltage in the secondary coil is lower than the voltage in the primary coil. This is used to reduce voltage for safe use in homes and appliances.

The iron core plays a crucial role in the transformer's operation. It concentrates and guides the magnetic flux produced by the primary coil, ensuring that the magnetic field links efficiently with the secondary coil. Without the iron core, the magnetic flux would be weaker and less effective in inducing a voltage in the secondary coil. The iron core also reduces core losses, which are losses due to hysteresis and eddy currents in the core material.