Home / Topics / Magnetism & Induction
Transformer
Intermediate
Changes AC voltage using mutual induction.
V₂/V₁ = N₂/N₁Two coils on a shared core: V₂/V₁ = N₂/N₁. Step-up raises voltage and lowers current, keeping power nearly constant: V₁I₁ ≈ V₂I₂.
230 V to 12 V with 1000 turns primary: 52 turns secondary.
Only works with AC.
In more detail
A transformer uses mutual inductance between two coils wound on a common core to change voltage. The voltage ratio equals the turns ratio, Vs/Vp = Ns/Np.
Real-world uses
- Transformers step voltage up for transmission and down for homes.
- Phone chargers include small transformers.
- Power grids use transformers to step voltages up for long-distance transmission and down for homes.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why does a transformer need AC?
A steady DC current produces no changing flux, so no voltage is induced.
Does a transformer increase power?
No. Ideally power is conserved, so higher voltage means lower current.
Why does a transformer need AC?
A changing current is needed to produce a changing flux, and only a changing flux induces a voltage in the second coil.
Related topics in Magnetism & Induction
Inductance of a solenoid · Energy in an inductor · Mutual inductance · Transformer losses · AC generator · Dynamo and alternator