Q 12-07-028NEETJEE MainMedium
A transformer of efficiency $90\%$ steps $220$ V down to $22$ V and delivers $198$ W to a load. The current in the primary is
Answer: (C) $1$ A
Concept. Input power $= \dfrac{\text{output power}}{\text{efficiency}}$; then $I_p = \dfrac{P_{\text{in}}}{V_p}$.
Step 1. Input power. $\dfrac{198}{0.9} = 220$ W.
Step 2. Primary current. $\dfrac{220}{220} = 1$ A.
Answer. $1$ A (Option C).
Solution by Sreeraj P, M.Sc Physics