Electric power is generated at large plants, transmitted over long distances, and then delivered to residences. Which option best describes the overall voltage level change from generation through transmission to residential supply?

Introduction:
Power systems use transformers and transmission lines to move energy efficiently from generating stations to end users. Understanding why voltages are stepped up and then stepped down is a core concept in power engineering and safety.

Given Data / Assumptions:

• Generation at a plant, long-distance transmission, and local distribution to homes.
• Use of transformers for stepping voltage levels up or down.
• Goal: minimize losses while ensuring safe delivery.

Concept / Approach:
Transmission losses are proportional to I^2 * R. For a given power P, increasing voltage V reduces current I since P = V * I. Therefore, power is transmitted at high voltage (and correspondingly lower current) to reduce losses and conductor size. Near consumers, transformers step voltage down to safe levels (e.g., 230 V rms) for residential use.

Step-by-Step Solution:
At the plant, generators feed step-up transformers to raise voltage to transmission levels (tens to hundreds of kV).High-voltage lines carry power over long distances with reduced current and lower I^2 * R losses.Substations use step-down transformers to medium voltage for distribution networks.Local transformers further reduce to low-voltage service (e.g., 230/120 V) for residential loads.

Verification / Alternative check:
Utility grid diagrams and standards consistently show transmission at high voltages (e.g., 110 kV, 220 kV, 400 kV) and distribution to homes at low voltage. This architecture is universal because it is efficient and safe.

Why Other Options Are Wrong:

• High→High or Low→Low: Do not reflect the necessary step-down for residential safety and appliance ratings.
• Low→High: Opposite of the actual overall path to homes.
• Medium→Medium: Not representative of the full generation-to-home journey.

Common Pitfalls:

• Confusing transmission voltage levels with distribution service voltages.
• Assuming higher voltage always means more power; power depends on both voltage and current.

Final Answer:
high voltage to low voltage