What is the principle of a transformer?

Short Answer:

The principle of a transformer is based on electromagnetic induction, specifically mutual induction. When alternating current (AC) flows through the primary coil, it produces a changing magnetic field. This changing magnetic field passes through the secondary coil and induces an electromotive force (EMF) in it.

This process allows electrical energy to be transferred from one circuit to another without any physical connection. The transformer works only with AC because a changing magnetic field is required to induce voltage. It is used to increase (step-up) or decrease (step-down) voltage in power systems.

Detailed Explanation:

Principle of a transformer

A transformer is a static electrical device that works on the principle of mutual electromagnetic induction. This principle was discovered by Michael Faraday, and it states that a changing magnetic field in one coil induces a voltage in another nearby coil. In transformers, these coils are called the primary winding and the secondary winding, and they are wound around a common magnetic core.

The transformer transfers electrical energy from the primary coil to the secondary coil through the magnetic field, without any direct electrical connection. The core helps to efficiently link the magnetic flux between the two windings. The operation relies completely on alternating current (AC) because a changing current is needed to produce a changing magnetic field, which is essential for induction.

Working steps of the principle

  1. AC in primary coil:
    When AC is applied to the primary winding, it creates an alternating magnetic field around it.
  2. Magnetic flux in the core:
    This magnetic field is confined and guided through the iron core to the secondary winding, ensuring maximum flux linkage.
  3. EMF induced in secondary coil:
    According to Faraday’s Law, this changing magnetic flux in the secondary coil induces an EMF. This EMF causes current to flow if the secondary is connected to a load.
  4. Voltage transformation:
    The ratio of the voltages between the secondary and primary coils is determined by the number of turns in each winding.

VsVp=NsNp\frac{V_s}{V_p} = \frac{N_s}{N_p}Vp​Vs​​=Np​Ns​​

Where:

    • VsV_sVs​, VpV_pVp​ are voltages
    • NsN_sNs​, NpN_pNp​ are number of turns in secondary and primary coils
    • If Ns>NpN_s > N_pNs​>Np​: step-up transformer
    • If Ns<NpN_s < N_pNs​<Np​: step-down transformer

Conditions for efficient working

  • Only AC can be used, as DC doesn’t create changing magnetic fields.
  • The core must be magnetic, usually soft iron, to concentrate and guide magnetic lines.
  • Tight coupling between coils ensures better energy transfer.
  • Insulation between coils is essential to prevent short circuits.

Applications of this principle

  • Power transmission: Step-up and step-down voltages to reduce energy loss.
  • Adapters and chargers: Convert high voltage to low voltage for electronic devices.
  • Electrical isolation: Separate sections of circuits for safety.
  • Measurement tools: Current transformers and voltage transformers in metering systems.
  • Induction heating: In cooking and industrial heating systems.
Conclusion:

The transformer operates on the principle of mutual electromagnetic induction. A changing magnetic field in the primary coil induces a voltage in the secondary coil. This principle enables safe, efficient transfer of electrical energy at different voltage levels. It plays a key role in electricity distribution, power systems, and electronic devices across industries.