Transformer ratios — in a step-down transformer, is the turns ratio Ns/Np less than 1? Assume turns ratio is defined as secondary turns divided by primary turns.

Introduction / Context:The turns ratio determines how a transformer changes voltage and current. A step down is used when a higher supply voltage must be reduced for a load, such as adapting mains to equipment levels. This item checks the sign and magnitude of the turns ratio for a step-down device.

Given Data / Assumptions:

• Turns ratio defined as Ns/Np, where Ns is secondary turns and Np is primary turns.
• Ideal transformer assumptions for clarity.
• Steady sinusoidal operation.

Concept / Approach:Voltage ratio follows Vs/Vp = Ns/Np. For a step-down transformer, Vs < Vp, which requires Ns/Np < 1. Current ratio is inverse: Is/Ip = Np/Ns > 1. Thus, a step-down device has fewer secondary turns than primary turns and consequently a turns ratio less than one under the given definition.

Step-by-Step Solution:

Verification / Alternative check:Example: Np = 1000 turns, Ns = 100 turns → Ns/Np = 0.1. With Vp = 230 V, ideal Vs = 23 V, clearly a step down. Current is stepped up by 10 times ideally.

Why Other Options Are Wrong:

• Marking “False” generally results from using the inverse definition (Np/Ns). Under that alternate definition, a step-down transformer has a ratio greater than one. The statement here explicitly uses Ns/Np.

Common Pitfalls:Ambiguity in how ratio is quoted. Always specify whether you mean Ns/Np or Np/Ns when comparing devices to avoid misinterpretation in specifications and procurement.

Final Answer:True