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

JEE Main · 2024 · 09 Apr 2024 · Shift 1 · Electromagnetic Induction

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

)

Answer: 10

Solution

DC:

R = \frac{20}{5} = 4 Ω

. AC:

Z = \frac{20}{4} = 5 Ω \Rightarrow X_{L} = 5^{2} - 4^{2} = 3 Ω

L = \frac{X _{L}}{2 π f} = \frac{3}{2 \times 3 \times 50} = 0.010

= 10

mH.

JEE Main · 2024 · 09 Apr 2024 · Shift 1 · Integer answer

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