What factor determines the turns ratio of a transformer?

• A. Primary current to secondary current
• B. Primary voltage to secondary voltage
• C. Transformer efficiency
• D. Transformer power rating

Answer: (B)

The turns ratio of a transformer is fundamentally determined by the relationship between the primary voltage and the secondary voltage. This ratio signifies how many turns of wire are present on the primary winding compared to the secondary winding. The basic principle states that the voltage across the windings of a transformer is proportional to the number of turns in those windings.

When there is an increase in the number of turns on the primary winding compared to the secondary winding, the transformer steps up the voltage from primary to secondary; conversely, if the secondary has more turns than the primary, the transformer steps down the voltage. This relationship is governed by the formula:

[

\frac{V_p}{V_s} = \frac{N_p}{N_s}

]

where (V_p) is the primary voltage, (V_s) is the secondary voltage, (N_p) is the number of turns in the primary coil, and (N_s) is the number of turns in the secondary coil.

Factors such as primary current to secondary current, transformer efficiency, or power rating are relevant in broader contexts of transformer operation and design but do not directly influence the turns ratio, which is solely determined by the voltages involved. Understanding this relationship