All questions of Sources of Energy for Class 10 Exam

Wind power is the amount of electrical energy that can be generated by a windmill. It is important to understand the factors that affect wind power to optimize the efficiency of wind turbines and maximize their energy generation. The wind speed and the radius of the windmill's blades are two of the key factors that determine wind power.

**Wind Speed and Wind Power**
The wind speed directly affects the amount of power that can be generated by a windmill. As the wind blows faster, it exerts more force on the windmill's blades, causing them to rotate at a higher speed. This rotation generates more mechanical energy, which can be converted into electrical energy. Therefore, wind power is directly proportional to the wind speed.

**Mathematical Relationship**
The mathematical relationship between wind power and wind speed can be described by an equation. According to scientific research and empirical data, wind power is directly proportional to the cube of the wind speed. This means that if the wind speed doubles, the wind power will increase by a factor of eight (2^3). Similarly, if the wind speed triples, the wind power will increase by a factor of twenty-seven (3^3).

**Explanation of Option B**
Option B states that wind power is directly proportional to the cube of the wind speed. This is the correct answer because it accurately describes the relationship between these two variables. The cube of the wind speed represents the exponential increase in wind power as the wind speed increases. This relationship highlights the importance of harnessing high wind speeds to maximize the energy generation of windmills.

**Importance of Blade Radius**
While wind speed is a crucial factor in determining wind power, the radius of the windmill's blades also plays a significant role. The larger the radius, the more area the blades cover, resulting in a greater capture of wind energy. Therefore, wind power is also directly proportional to the radius of the blades. However, it is important to note that the relationship between wind power and blade radius is not as pronounced as the relationship between wind power and wind speed.

In conclusion, wind power is directly proportional to the cube of the wind speed. This relationship highlights the exponential increase in wind power as the wind speed increases. Additionally, the radius of the windmill's blades also affects wind power, although to a lesser extent. By understanding these relationships, wind turbine designers and operators can optimize the efficiency and energy generation of windmills.

Wood is a renewable source of energy because it is derived from trees, which can be replanted and grown again. This makes it a sustainable source of energy that can be harvested without depleting the resource.
- Renewable Nature of Wood:
Wood is considered renewable because trees can be replanted and grown over time, unlike fossil fuels which take millions of years to form.
- Carbon Neutrality:
When wood is burned for energy, it releases carbon dioxide into the atmosphere. However, this carbon dioxide is re-absorbed by new trees that are planted, making wood a carbon-neutral energy source.
- Sustainable Forestry Practices:
To ensure that wood remains a renewable source of energy, sustainable forestry practices must be followed. This includes planting new trees to replace those that are harvested and managing forests in a way that maintains biodiversity.
- Benefits of Wood Energy:
Using wood as a source of energy has several benefits, including being a cost-effective and widely available resource. It can also help reduce reliance on non-renewable sources of energy like coal and oil.
In conclusion, wood is indeed a renewable source of energy due to its ability to be replenished through sustainable forestry practices. By utilizing wood for energy production in an environmentally responsible manner, we can help reduce the impact of climate change and move towards a more sustainable energy future.

There are several countries that are commonly referred to as "the land of the rising sun," but the most commonly known one is Japan.

Explanation:

Conventional sources of energy:
Conventional sources of energy are those that have been widely used for a long time and are the primary sources of energy for most human activities. These sources are primarily derived from fossil fuels, which include coal, oil, and natural gas. Other conventional sources of energy include hydro energy and biomass energy.

- Fossil fuel: Fossil fuels are the most widely used conventional sources of energy. They are formed from the remains of plants and animals that lived millions of years ago. Fossil fuels are burned to release energy in the form of heat or electricity.

- Biomass energy: Biomass energy is derived from organic matter, such as plants and agricultural waste. It can be used directly as a fuel or converted into other forms of energy, such as biogas or biofuels. Biomass energy is considered a conventional source because it has been used for centuries.

- Hydro energy: Hydro energy, also known as hydroelectric power, is generated by harnessing the power of flowing or falling water. It is a clean and renewable source of energy that has been used for many years. Hydroelectric power plants convert the energy of moving water into electricity.

Non-conventional source of energy:
- Solar energy: Solar energy is the energy derived from the sun. It is considered a non-conventional source because it does not rely on the burning of fossil fuels or the use of mechanical processes. Solar energy can be harnessed through the use of photovoltaic cells or solar thermal systems to generate electricity or heat.

Conclusion:
Based on the information provided, the correct answer is option 'B' - Solar energy. Solar energy is a non-conventional source of energy, as it does not rely on the burning of fossil fuels or mechanical processes. It is considered a renewable and sustainable source of energy that has gained significant attention in recent years due to its environmental benefits.