JEE Main 2016 · 3 Apr · Shift 1 · Physics Q17

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PhysicsSingle correct+4 / -1Question 17 of 90

An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to :

80 H

0.08 H

0.044 H

0.065 H

Answer and worked solution

Official answer: D

The lamp's resistance is $\frac{80}{10}=8$ Ω, and $Z=\frac{220}{10}=22$ Ω is needed. So $X_L=\sqrt{22^2-8^2}=\sqrt{420}\approx20.5$ Ω and
$L=\frac{20.5}{2\pi\times50}\approx0.065\text{ H}.$

Topics:Reactance and impedance

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JEE Main 2016 · 3 Apr · Shift 1, Physics question 17