JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Alternating Current

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A common transistor radio set requires 12 V (D.C) for its operation. The D.C source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V (A.C) on standard domestic A.C supply. The number of turns of secondary coil are 24, then the number of turns of primary are ______.

Answer: 440

Solution

For an ideal transformer, the voltage ratio equals the turns ratio:

\frac{V _{p}}{V _{s}} = \frac{N _{p}}{N _{s}}

Given:

$V_{p} = 220$ V (primary voltage)
$V_{s} = 12$ V (secondary voltage)
$N_{s} = 24$ (secondary turns)

N_{p} = N_{s} \times \frac{V _{p}}{V _{s}} = 24 \times \frac{220}{12} = 24 \times 18.33... = 440

Answer: 440

JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Integer answer

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