How does an electrical transformer work?

A transformer uses AC current in a primary coil to generate a constantly changing magnetic field in an iron core. This changing magnetic field passes through a secondary coil, inducing an AC voltage according to the turns ratio.

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Core Study Guide

Electromagnetism & Induction

The unification of electric and magnetic fields.

Electromagnetism describes how electric currents generate magnetic fields, and how changing magnetic fields induce voltages.

This unit covers Ampere's Law, Faraday's Law of Induction, Lenz's Law, and their applications in transformers and AC generators.

Key Takeaways

•An electric current flowing through a wire generates a concentric magnetic field around it.
•Faraday's Law states that a changing magnetic flux induces an electromotive force (EMF).
•Lenz's Law states that induced current opposes the change in magnetic flux that created it.

Core Concepts & Definitions

1Faraday's Law of Induction

Any change in the magnetic environment of a coil of wire will cause a voltage (EMF) to be induced in the coil.

•EMF = -N * (ΔΦ / Δt).

•Flux Φ = B * A * cos(θ).

2Lenz's Law

The direction of the induced current is always such that its own magnetic field opposes the original change in flux.

•Represented by the negative sign in Faraday's equation.

•A consequence of the conservation of energy.

Quick Revision Notes

•Magnetic flux (Φ) is measured in Webers (Wb). 1 Wb = 1 T·m².
•Step-up transformers increase voltage but decrease current to maintain power conservation.