Efficient Voltage Conversion
A transformer is a passive electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two coils of wire (Primary and Secondary) wrapped around a common iron core.
Transformers are the reason we can have an electrical grid. They allow us to step up voltage for efficient long-distance transmission and step it back down to safe levels ($120 , \text{V}$ or $230 , \text{V}$) for use in homes.
The Transformation Ratio
The ratio of the voltages is exactly equal to the ratio of the number of turns in the coils.
- Step-Up Transformer: Has more turns on the secondary side, increasing voltage.
- Step-Down Transformer: Has fewer turns on the secondary side, decreasing voltage.
- Energy Balance: Because energy is conserved, if a transformer increases voltage, it must decrease current by the same ratio ($P = V \cdot I$).
The Formula
Example Calculation
A transformer has $500$ turns on the primary side and $50$ turns on the secondary. You plug the primary into a $120 , \text{V}$ wall outlet.
- Turns Ratio ($N_s / N_p$): $50 / 500 = 0.1$.
- Secondary Voltage ($V_p \times \text{Ratio}$): $120 \times 0.1 = 12 , \text{V}$.
This is a $10:1$ step-down transformer, outputting $12 , \text{V}$.