An arc lamp requires a direct current of 10 A and 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:

- 0.08 H
- 0.044 H
- 0.065 H
- 80 H

**Solution**

For the lamp with direct current,

V = IR

R = 8 Ω

X_{L} = Lω = L × (2πf) = L × 100π

\( Z = \sqrt{8^2+(L \times (100 \pi))^2} \)

\( Z = \dfrac{V_{rms}}{I_{rms}} = \dfrac{220}{10} \)

484 = 64 + 10^{4}(π^{2}L^{2})

L = 0.065 H

**The correct option is C.**