Question

Electric power station 100 MW transmits power to a distant load through long and thin cables which of the following modes of transmission would result in less power wastage

A) 20,000 V

B) 200 V

Answer 1

Power P = 100 MW

1)Current in the cable when power is transmitted at 20000 V will be'

we know P=IV

I=(100×10^6)÷(20,000)=5000 A

Power dissipation in this case: I^2.R=(5000)^2×R (where R is the resistance of cables)

2)Current in the cable when power is transmitted at 200 V will be

I'=(100×10^6)÷(200)=500000 A

Power dissipation in this case: I'^2.R
=(500000)^2.R

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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