An electric power station (100MW) transmits power to distant load through long and thin cable .

which of the two modes of transmission would result in lesser power wastage : power transmission of: (i)20000V or (ii)200V ?

Power P = 100 MW
Current in the cable when power is transmitted at 20000 V will be'
I=100×10620,000=5000 A
Power dissipation in this case: I2R=50002R  (where R is the resistance of cables)

Current in the cable when power is transmitted at 200 V will be
I'=100×106200=500000 A
Power dissipation in this case: I'2R=5000002R  
Comparing the two, we can see that power dissipation is much less in first case. So (i) will be correct choice.

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