Assertion (A): The velocity factor (VF) of a transmission line is the ratio of wave (phase) velocity on the line to the speed of light in vacuum. Reason (R): If the conductors are immersed in a non-magnetic insulating liquid (relative permittivity > 1), the wave velocity increases. Choose the correct option about A and R.

Introduction:
Velocity factor describes how fast an electromagnetic wave propagates along a transmission line relative to light in vacuum. It depends primarily on the line's effective permittivity and permeability.

Given Data / Assumptions:

• Non-magnetic medium: mu_r ≈ 1
• Insulating liquid has epsilon_r > 1
• VF = v/c where v is phase velocity on the line

Concept / Approach:
Phase velocity v = c / sqrt(epsilon_r * mu_r). For non-magnetic media, mu_r ≈ 1, so v ≈ c / sqrt(epsilon_r). Increasing epsilon_r decreases v, therefore VF decreases when immersed in a higher-permittivity dielectric.

Step-by-Step Solution:

Verification / Alternative check:
Typical coaxial cables with solid polyethylene (epsilon_r ≈ 2.25) have VF ≈ 0.66, confirming reduced velocity in higher-permittivity dielectrics.

Why Other Options Are Wrong:

• A/B: R is not true, so these cannot be correct.
• D: A is not wrong.

Common Pitfalls:
Confusing refractive index effects; assuming any insulating medium increases speed.

Final Answer:
A is correct but R is wrong