How is the turns ratio in a transformer calculated?

• A. Vp/Vs = Ns/Np
• B. Vp/Ns = Vs/Np
• C. Np/Vp = Vs/Ns
• D. Np/Ns = Vs/Vp

Answer: (A)

The turns ratio in a transformer is fundamental to understanding the relationship between the primary and secondary windings. The correct formulation is given by the equation Vp/Vs = Ns/Np, where Vp is the primary voltage, Vs is the secondary voltage, Np is the number of turns in the primary winding, and Ns is the number of turns in the secondary winding.

This equation signifies that the ratio of the primary voltage to the secondary voltage is equivalent to the ratio of the number of turns in the primary to the number of turns in the secondary. It reflects the principle of electromagnetic induction, demonstrating how changes in the number of winding turns impact the voltage levels while maintaining the energy balance within the transformer.

Essentially, if a transformer has more turns on the secondary than on the primary, it will step up the voltage, whereas if there are more turns on the primary, it will step down the voltage. This relationship is crucial for designing and using transformers effectively in electrical systems.

The other options incorrectly express the relationships among voltage and turns, failing to convey the direct proportional relationship that exists according to transformer theory. Understanding this correct ratio helps in the analysis and functioning of transformers in various applications.