## Book: Lakhmir Singh & Manjit Kaur - Physics

### Chapter: 3. Sources of Energy

#### Subject: Physics - Class 10th

##### Q. No. 39 of Questions Based on High Order Thinking Skills (HOTS)-Pg-142

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##### A large coal-fired power station producers 2000 MW of electrical energy. A wind turbine with 33 m blades can produces 300 kW.(a) How many turbines would be needed to replace the power station?(b) Why, in actual practice, this number of turbines could not replace the coal-fired power station?

(a) Electrical energy produced by coal-fired plant,

= 2000MW

= 2000x106W

Electrical energy produced by wind turbine

= 300kW

= 300x103W

No. of wind turbine required,

= 2000x106/300x103 = 6666.6

Hence, 6667 wind turbines would be needed to replace the power station.

(b) In actual practice, this no. of wind turbines could not replace the coal-fired power plant because the efficiency of wind turbines keeps changing due to changes in wind speed but the efficiency of steam turbines used in coal-fired power stations remains the same.

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