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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The Surge impedance of 50 miles long underground cable is 50Ω. For a 25 miles length it will be
25 Ω
50 Ω
100 Ω
None of above
50 Ω
B is correct because the surge impedance is a characteristic property determined by the line's distributed parameters (L and C) per unit length, making it independent of the total length.
Surge impedance of 50 miles long underground cable is 50Ω.
Zc=CL
Identify the Definition of Surge Impedance
The surge impedance (or characteristic impedance) of a transmission line or cable is defined by its distributed parameters, inductance (L) and capacitance (C) per unit length.
Zc=CL
Analyze Parameter Dependency
Since L and C are parameters defined per unit length (e.g., Henrys per meter and Farads per meter), the ratio L/C remains constant regardless of the total length of the cable.
Zc=constant
Calculate for New Length
Because the surge impedance is independent of the length of the cable, changing the length from 50 miles to 25 miles does not change the surge impedance value.
Zc(25 miles)=50 Ω
B is correct because the surge impedance is a characteristic property determined by the line's distributed parameters (L and C) per unit length, making it independent of the total length.
This concept is similar to 'Characteristic Impedance' in communication systems; remember that surge impedance relates to the traveling wave phenomena rather than steady-state power flow.