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'
$I=\frac{100\times {10}^6}{20,000}=5000 A$
Power dissipation in this case: $I^{2}R={\left(5000\right)}^{2}R (where R is the resistance of cables)$

Current in the cable when power is transmitted at 200 V will be
$I\text{'}=\frac{100\times {10}^6}{200}=500000 A$
Power dissipation in this case: $I{\text{'}}^{2}R={\left(500000\right)}^{2}R$
Comparing the two, we can see that power dissipation is much less in first case. So (i) will be correct choice.