When work is done on an object, energy is transferred. Power is the amount of work done in one second. Efficiency is a measure of how much useful energy is converted.
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A wind generator has an output power of 2.5 MW.
How long does it take to generate 250 GJ of electrical energy?
power = \(\frac{\text{energy transferred}}{\text{time taken}}\)
time taken = \(\frac{\text{energy transferred}}{\text{power}}\)
power = 2.5 MW = 2.5 x 1,000,000 W = 2,500,000 W
(1 MW = 1,000,000 W)
energy transferred = 250 GJ = 250 x 1,000,000,000 J = 250,000,000,000 J
(1 GJ = 1 000 000 000 J)
time taken = \({250,000,000,000 J}\div{2,500,000 W}\)
time taken = 100,000 s
100,000 s = \({100,000}\div{60}\) = 1666.7 minutes
1667 minutes = \({1667}\div{60}\) = 27.8 hours.
It takes the wind generator 27.8 hours.