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 values:

$\text{Efficiency} = \left( \frac{2.2 \text{ kJ}}{6.2 \text{ kJ}} \right) \times 100 = 35.48\%$

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

One reason is that not all of the air may hit the blade of the turbine, meaning some kinetic energy is not converted into electrical energy. Additionally, some energy is always lost due to friction and other factors in the turbine system.

Nuclear fission involves the splitting of a heavy nucleus (like Uranium) by a neutron, releasing energy, along with two daughter nuclei and more neutrons, which can lead to a chain reaction. It is already in use for electricity generation but poses challenges like radioactive waste disposal and the potential for accidents.

Nuclear fusion, on the other hand, involves the joining of light nuclei (like Hydrogen) under extreme conditions of temperature and pressure to form helium and release energy. Although fusion does not produce harmful waste, it has not yet been achieved on a practical scale and requires maintaining high energy conditions, making it technically challenging.

In summary:

• Fission: Splits nuclei, generates waste, riskier; Fusion: Joins nuclei, cleaner, but technically difficult.