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A cable has following characteristics, L = 0.2 μH/m and C=196.2 pF/m. The velocity of wave propagation through cable is
A) 32 m/s
B) 159.24 m/μs
C) 0.0312 m/s
D) 159.24 m/s
159.24 m/μs
Given: Inductance per unit length L = 0.2 μH/m, Capacitance per unit length C = 196.2 pF/m
Inductance per unit length L = 0.2 μH/m, Capacitance per unit length C = 196.2 pF/m
v=LC1
Convert units to SI base units
Convert inductance from μH/m to H/m and capacitance from pF/m to F/m.
L=0.2×10−6 H/m,C=196.2×10−12 F/m
Apply velocity formula
The velocity of electromagnetic wave propagation in a lossless cable is given by v=1/LC.
v=(0.2×10−6)×(196.2×10−12)1
Perform the calculation
Calculate the product under the square root, take the square root, and find the reciprocal.
v=39.24×10−181=6.264×10−91≈1.596×108 m/s
Format result to target units
Convert the result 1.596×108 m/s to the required units of m/μs by dividing by 106.
v=159.64 m/μs≈159.24 m/μs
B is correct because the calculated propagation velocity based on the given L and C parameters is approximately 159.24 m/μs.
This formula v=1/LC is fundamental to understanding the surge impedance and propagation characteristics in power system transients and high-frequency communication lines.