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ElectricalPower System

Reflection coefficient of the wave of load connected to a transmission line of surge impedance equal to that of transmission line is

Zero

Infinity

Correct Answer

⚙️ TE • Technical Concept & PrincipleElectricalPower System

Option C

Zero

Quick Summary:

The reflection coefficient ( $\Gamma$ ) represents the ratio of the reflected voltage wave to the incident voltage wave at the junction of a transmission line and a load. When the load impedance ( $Z_L$ ) is exactly equal to the surge impedance ( $Z_0$ ) of the transmission line, the load is said to be perfectly matched, resulting in zero reflection.

⚙️TETechnical SolutionConcept & Principle

💡 Explanation

🔢 Key Formulas

$\Gamma = \frac{Z_L - Z_0}{Z_L + Z_0}$ — Definition of Voltage Reflection Coefficient

$V_{reflected} = \Gamma V_{incident}$ — Relation between incident and reflected waves

⚙️ Working Principle

Reflection occurs at a discontinuity where the wave encounters an impedance mismatch. The reflection coefficient is defined as $\Gamma = \frac{Z_L - Z_0}{Z_L + Z_0}$ . When $Z_L = Z_0$ , the numerator becomes $(Z_0 - Z_0) = 0$ , leading to a total absorption of the incident wave by the load without any reflection back to the source.

📌 Key Points

▸
Impedance matching prevents signal degradation and standing waves.
▸
A matched transmission line transfers maximum power to the load.
▸
If $Z_L = \infty$ (open circuit), $\Gamma = 1$ .
▸
If $Z_L = 0$ (short circuit), $\Gamma = -1$ .

✅ Advantages

▸
Eliminates standing waves on the line
▸
Prevents destructive interference in communication signals

❌ Disadvantages / Limitations

▸
Requires precise components for exact matching
▸
Sensitivity to frequency variations in load impedance

🛠️ Applications / Uses

▸
RF transmission line terminations
▸
Power system protection relays
▸
Antenna feeder systems

📄 Additional Information

▸
The surge impedance $Z_0$ of a transmission line is given by $\sqrt{\frac{L}{C}}$ .
▸
Option A and B are identical in the prompt, but since the result is zero, they remain incorrect.

📊 Diagram / Illustration

✅

C is correct — When the load impedance is matched to the surge impedance, the reflection coefficient becomes zero as there is no discontinuity to cause wave reflection.

Core Concepts Used

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Surge Impedance Transmission Line Transients Reflection Coefficient

💡 EXAM TIP

Always remember that for a matched line, the reflection coefficient is 0, but the transmission coefficient is 1.

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