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The output of a step-down transformer is measured to be 24 V when connected to a 12 W light bulb. The value of the peak current (Iₘ) is _____.

Asked in GUJCET 2023 · RMS and mean values

• (1) 1.41 A
• (2) 0.71 A
• (3) 2 A
• (4) 2.83 A

Step-by-step solution

Why the other options are wrong

• (1) Needs two slips: the ratio upside down, (24)/(12)=2, and then a division by √2 instead of a multiplication: 2/(√2)=1.41 A.
• (3) Takes the ratio upside down, V/P=(24)/(12)=2, and stops there without converting to a peak. Current is power divided by voltage.
• (4) Converts to the peak correctly but starts from the ratio upside down: √2×(24)/(12)=2.83 A. The r.m.s. current is P/V=0.5 A.

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