Transmission lines — identify the secondary (derived) constants Which of the following are called the secondary constants of a uniform transmission line?

Introduction / Context:
Transmission lines are characterized by two sets of parameters. The primary (distributed) constants are resistance per unit length R, inductance per unit length L, conductance per unit length G, and capacitance per unit length C. From these, we derive the so-called secondary (or derived) constants that govern wave behavior along the line: the characteristic impedance Z0 and the propagation constant γ. This question asks you to correctly identify the secondary constants.

Given Data / Assumptions:

• Uniform, linear transmission line.
• Primary constants: R, L, G, C (functions of frequency in general).
• Secondary constants are defined from the primaries.

Concept / Approach:
Z0 and γ are obtained from (R, L, G, C):

These two fully describe how signals propagate and reflect: Z0 sets the impedance seen by a traveling wave; γ sets attenuation α and phase constant β, hence wave velocity v_p = ω/β. While wave velocity is an important quantity, it is not a fundamental secondary constant; it is derived from γ (v_p = ω/β) and thus considered a consequence, not a defining parameter.

Step-by-Step Solution:

Verification / Alternative check:
Any handbook or EM textbook defines “secondary” precisely as Z0 and γ because they are the two independent line descriptors obtained from the four primaries.

Why Other Options Are Wrong:

• A: Lists only Z0 and omits γ.
• C: Adds wave velocity, which is derived from γ, not a separate secondary constant.
• D: Includes L, which is a primary constant, not secondary.

Common Pitfalls:
Confusing “derived from” (like v_p from β) with being a fundamental secondary constant; mixing primaries with secondaries.

Final Answer:
Z0 and γ