What is the basic principle that allows a transformer to work

• A. Induction
• B. Conduction
• C. Polarization
• D. Resonance

Answer: (A)

Electromagnetic induction is the basic idea behind how a transformer works: when the current in the primary winding changes, it creates a changing magnetic flux that links to the secondary winding, inducing a voltage there. This is described by Faraday’s law, emf = -N dΦ/dt, where the induced voltage depends on how many turns the coil has and how quickly the flux changes. The magnetic core helps concentrate the flux so the secondary sees strong coupling, allowing energy to move from the input circuit to the output circuit without a direct wire connection. The turns ratio then sets whether the voltage is stepped up or down, while real transformers also have losses that affect efficiency. Alternatives don’t fit because conduction requires a direct electrical path between the circuits, polarization relates to dielectric response in materials, and resonance involves matching frequencies in a circuit rather than transferring energy between isolated coils.