Transformers: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Transformers. Understanding the underlying formula is key to arriving at the correct answer below:

Input power is $P_{in} = 3000 W$, so primary current $I_p = \frac{P_{in}}{V_p} = \frac{3000}{200} = 15 A$.
Transformer efficiency is $\eta = \frac{P_{out}}{P_{in}} = \frac{V_s I_s}{P_{in}}$.
Substitute values: $0.90 = \frac{V_s \times 6}{3000}$, which gives secondary voltage $V_s = \frac{2700}{6} = 450 V$.