Question

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

• A. 0.37 A
• B. 0.27 A
• C. 2.7 A
• D. 3.7 A

Answer 1

Answer: (B)

0.27 A

Answer 2

$V_sI_s=V_pI_p$ (ideal transformer)

$\Rightarrow P_{out}=P_{in}$

$60=220\times I_p$

$I_p=\frac{60}{220}=0.27A$

So, the correct answer is option (B): 0.27A