In order to reduce the energy loss along the transmission the utility power line
ID: 1791496 • Letter: I
Question
In order to reduce the energy loss along the transmission the utility power line is usually kept high voltage (thousands of volts) much higher than the domestic voltage. A student argued that the power loss along the utility line is 12r where r is the resistance along the transmission line. Applying the Ohm's law this is also equal to V2lr. So it does not matter, either keeping the voltage low or current low will reduce the energy loss along the transmission line. Do you agree with this? If you do not agree explain why. Since utility voltage are AC assume voltage or current are average over several cycles. "Hint the power delivered from the power station varies depending on the domestic usage. Assume the power demand by users at particular instant is constant.) (d )Explanation / Answer
For long transmission we use high voltage in order to reduce power loss.
Assume the power to be transmitted is P, and the resistance of the transmission line is r.
If the power is transmitted with voltage V, then the current flow through the transmission line is I=P/V.
The power loss Ploss=I2*r=(P/V)2*r
Since P and r are fixed conditions, less power will be lost if high voltages V are used.