A 12 V, 60 W lamp is connected to the secondary winding of a step down transformer, whose Primary winding is connected to AC mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding?
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Question

A 12 V, 60 W lamp is connected to the secondary winding of a step down transformer, whose Primary winding is connected to AC mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding?

Options

G1 Physics · Accepted Answer

Step 1: The lamp draws secondary power Pₛ=60W at Vₛ=12V. Step 2: For ideal transformer Pₚ=Pₛ, so Iₚ=Pₚ/Vₚ. Step 3: Iₚ=60W/220V=0.273A≈0.27A. Answer C. Final answer: (C) 027A.