Which of the following practices will lead to losses in electrical power transmission?

Analyze the question: We need the practice that causes power loss during transmission.

Concept: Power lost in transmission cables is due to the heating effect of current (Joule heating):

P_loss = I²R

So the loss depends on the square of the current flowing and the resistance of the cable.

Also, the power being transmitted is P = IV. For a fixed power, if voltage V is low, current I must be high.

Evaluate each option:

• A. Large-diameter cables: A larger cross-sectional area gives lower resistance (R = ρL/A), so I²R is reduced. This reduces losses.
• B. High voltage, low current: Since I is small, I²R is small. This reduces losses. It is the reason the national grid transmits at very high voltages (e.g., 330 kV).
• C. Low voltage, high current: Since I is large, I²R becomes very large. Much of the energy is lost as heat in the cables. This causes losses.
• D. Step-up transformer at the production end: This raises the voltage and lowers the current, so it reduces losses. (The option says "set-up", but it means "step-up".)

Answer: The practice that leads to losses is transmitting at relatively low voltage and high current, which is option C.

Exam tip: Remember "High Voltage, Low Loss". Because loss = I²R, always think of reducing the current. Anything that lowers I (stepping up voltage) or lowers R (thick cables) saves power. Anything that raises I or R wastes power.