When a coil is connected across a 20 V dc supply, it draws a current of 5 A. When it is connected across 20 V, 50 Hz ac supply, it draws a current of 4 A. The self inductance of the coil is __________ mH. (Take π = 3) Numerical answer type. Work it out, then open the answer.

Answer: 10. DC: R = 20/5 = 4 Ω. AC: Z = 20/4 = 5 Ω. XL = √(5² - 4²) = 3 Ω L = (XL)/(2π f) = (3)/(2 × 3 × 50) = 0.01 H L = 10 mH

When a coil is connected across a 20 V dc supply, it draws a current… | JEE Main 2024 (9 Apr, Shift 1)

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RL and RC Series Circuits

When a coil is connected across a $20\text{ V}$ dc supply, it draws a current of $5\text{ A}$ . When it is connected across $20\text{ V},\ 50\text{ Hz}$ ac supply, it draws a current of $4\text{ A}$ . The self inductance of the coil is __________ $\text{mH}$ . (Take $\pi = 3$ )

Numerical answer type. Work it out, then open the answer.

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Answer: 10

DC: $R = \frac{20}{5} = 4\ \Omega$ . AC: $Z = \frac{20}{4} = 5\ \Omega$ .
$X_L = \sqrt{5^2 - 4^2} = 3\ \Omega$
$L = \frac{X_L}{2\pi f} = \frac{3}{2 \times 3 \times 50} = 0.01\text{ H}$
$L = 10\text{ mH}$

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