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NEET PHYSICSMedium

A 12 V12\text{ V}, 60 W60\text{ W} lamp is connected to the secondary of a step-down transformer, whose primary is connected to ac mains of 220 V220\text{ V}. Assuming the transformer to be ideal, what is the current in the primary winding?

A

0.27 A

B

2.7 A

C

3.7 A

D

0.37 A

Step-by-Step Solution

For an ideal transformer, input power equals output power. Pin=Pout=60 WP_{in} = P_{out} = 60\text{ W}. Since Pin=Vp×IpP_{in} = V_p \times I_p, we have 60 W=220 V×Ip60\text{ W} = 220\text{ V} \times I_p. Thus, Ip=60220≈0.27 AI_p = \frac{60}{220} \approx 0.27\text{ A}.

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