Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to

1. Analyze the question

The question asks why power is transmitted at high voltage. The reason is to reduce the energy lost along the transmission lines, and we need to identify what that loss is due to.

2. Concept

Power transmitted: P = IV

For a fixed power P, a higher voltage V means a smaller current I = P/V.

The power lost in the cables is the heating effect of current (Joule heating):

P_loss = I²R

Substituting I = P/V:

P_loss = (P/V)² × R

So if V is increased, the current drops and the heat loss falls with the square of the current.

3. Working through the options

• A. Heat dissipation: Correct. The main energy loss in transmission lines is I²R heating in the wires. High voltage means low current, so less heat is lost.
• B. Eddy currents: These occur in transformer cores, not in the transmission lines. They are reduced by laminating the core and have nothing to do with the choice of transmission voltage.
• C. Excessive current discharge: This is not a standard physics term, and the loss is not a "discharge".
• D. Excessive voltage discharge: Also not the reason. High voltage actually brings insulation challenges, but it is chosen despite this.

4. Answer

The energy loss in transmission is due to heat dissipation (I²R loss), which is minimized by sending power at high voltage and low current.

5. Exam tip

Remember the chain: High V → Low I → Low I²R → Less heat loss. Any question on "why high voltage for transmission" nearly always points to reduced heating loss in the cables. Eddy currents belong to the "transformer core" questions.