Question

11 kW of electric power can be transmitted to a distant station at (i) 220 V (ii) 22000 V. Which of the two transmission modes be preferred and why ? Support your answer with calculations.

Answer 1

Here, `E_(p) xx I_(p) = 11 kW = 11000 W`
(i) When power is transmitted at `E_(s) = 220 V`
`I_(s) = (E_(p) I_(p))/( E_(s)) = (11000)/(220) = 50 A`
Energy lost a heat `= I_(s)^(2) R = (50)^(2) R`
`= 2500 R` watt
(ii) When power is transmitted at
`E_(s) = 22000 V`
`I_(s) = (E_(p) I_(p))/(E_(s)) = (11000)/(22000) = 0.5 A`
Energy lost as heat `= I_(s)^(2) = (0.5)^(2) R = 0.25 R` watt which is much less than energy loss in case (i). Therefore, power transmission should be done at 22000 V.