If electrical power is transmitted over long distance, the resistance of the wire become significant. Why? Which mode of transmission would result in less power loss;high current and low voltage or low current and high voltage?discuss why?
When electrical power is transmitted over long distances, the resistance of the wire becomes significant due to the following reasons:
1. Length of the wire: As the distance of transmission increases, the length of the wire also increases. Since the resistance of a wire is directly proportional to its length (R = ρL/A, where R is resistance, ρ is resistivity, L is the length of the wire, and A is the cross-sectional area), a longer wire results in a higher resistance.
2. Material properties: The resistivity of the material used for the transmission wire also affects the resistance. Typical materials used for power lines, such as copper and aluminum, have low resistivity. However, over long distances, even low resistivity becomes significant and contributes to power loss.
3. Temperature: Resistance of a conductor also depends on its temperature. If the temperature increases, the resistance of the wire will increase. As current flows through the wire and losses occur due to the resistance, the wire heats up, further increasing the resistance and losses.
To minimize power loss in long-distance power transmission, it is more efficient to use low current and high voltage. This is because the power loss in a transmission line is proportional to the square of the current (P_loss = I^2R, where P_loss is the power loss, I is the current, and R is the resistance). By increasing the voltage and decreasing the current, the power loss due to resistance is reduced.
High voltage, low current transmission reduces the overall current flow in the transmission line, leading to a reduction in resistive losses (as power loss is a function of current squared). Moreover, it allows the use of smaller diameter conductors, reducing the requirement of bulky and heavy conductors for long-distance transmission. That is why long-distance power transmission typically uses high-voltage lines with voltages in the range of hundreds of kilovolts.