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GATE 2026 IN – Question 17

Electrical Circuits and Machines · Transformers and electrical machines · 1 mark · Multiple choice

A single-phase step-down transformer has a high-voltage primary winding and a low-voltage secondary winding. The secondary winding is connected to a load impedance $Z_2$. The impedance $Z_2$ when referred to the primary winding is denoted by $Z_2\prime$. Which of the following conditions is true?

  1. $Z_2\prime=Z_2$
  2. $0.5Z_2<Z_2\prime<Z_2$
  3. $Z_2\prime>Z_2$
  4. $Z_2\prime\le0.5Z_2$

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Correct answer: (C) $Z_2\prime>Z_2$

Explanation

Let $a=N_1/N_2=V_1/V_2$ be the ideal turns ratio. Voltage scales by $a$ and current by $1/a$, so the referred impedance is $Z_2\prime=a^2Z_2$.

For a step-down transformer, $a>1$, hence the load impedance is multiplied by a factor greater than one. Therefore **C** is intended. For a complex load, this comparison means the scaling factor or impedance magnitude; complex numbers themselves are not ordered.