10 (a) Figure 13 shows wind turbines, used to generate electricity for the National Grid - Edexcel - GCSE Physics - Question 10 - 2021 - Paper 1

To calculate the efficiency of the turbine, we use the formula:

$\text{Efficiency} = \left( \frac{\text{Energy Output}}{\text{Energy Input}} \right) \times 100$

Substituting the given values:

$\text{Efficiency} = \left( \frac{2.2 \text{ kJ}}{6.2 \text{ kJ}} \right) \times 100$

Calculating this gives:

$\text{Efficiency} = \left( 0.3548 \right) \times 100 = 35.48\%$

Thus, the efficiency of the turbine is approximately 35.5%.

It is impossible for the turbine to use all the kinetic energy of the wind because:

• Not all the air hits the blades of the turbine due to the flow pattern of the wind.