Characteristic Impedance Calculation

Correct Answer

B — 300Ω

Concept and Reasoning

For a nearly lossless overhead line, surge impedance Z0=√(L/C). With L=0.9 mH/km and C=10 nF/km, L/C=0.9×10⁻³/(10×10⁻⁹)=9×10⁴, so Z0=300 Ω. Thus option B.

Calculation / Key Relation

Z0=√(L/C)=√(0.9×10⁻³/10×10⁻⁹)=300Ω

Exam Takeaway

Use per-unit-length L and C in consistent units; the km cancels.

Common Mistake

Do not use √(C/L) or forget the milli/nano conversion.