CBSE Class 10 Science Chapter 14: Sources of Energy NCERT Solutions

Solution: A good source of energy possesses several key qualities that make it practical and sustainable for use. These include:

1. Easy Availability: It should be readily accessible and obtainable in sufficient quantities.
2. High Work Output: It should be capable of doing a large amount of work or producing significant heat per unit of its volume or mass.
3. Ease of Storage and Transport: It should be convenient to store safely and transport from its source to the point of use.
4. Economical: The cost associated with obtaining, processing, and using the energy source should be reasonable.
5. Low Environmental Pollution: It should cause minimal harm to the environment, producing little to no harmful pollutants when used.

Solution: A good fuel is one that effectively converts its stored energy into useful work or heat. Its primary characteristics are:

• It produces a large amount of heat when it burns (high calorific value).
• It burns easily and completely, ideally without producing excessive smoke or harmful by-products.
• It is easily available and accessible.
• It is relatively inexpensive.
• It is safe to handle, store, and transport.

Solution: For heating food, using LPG (Liquefied Petroleum Gas), CNG (Compressed Natural Gas), or electricity would be the most practical choices. The reasons for this preference are:

These sources offer high thermal efficiency, meaning they convert a large portion of their energy into heat effectively. They also tend to cause less environmental pollution compared to burning solid fuels like wood or coal. Furthermore, they are convenient to use, allowing for easy control over the heating process.

Solution: The use of fossil fuels like coal and petroleum comes with significant disadvantages:

• Air Pollution: Burning fossil fuels releases various pollutants into the atmosphere, including oxides of carbon, nitrogen, and sulfur.
• Acid Rain: The acidic oxides released can combine with atmospheric moisture to form acid rain, which damages water bodies, soil, and ecosystems.
• Greenhouse Effect: The combustion of fossil fuels releases large amounts of carbon dioxide (CO2), a major greenhouse gas that contributes to global warming and climate change.
• Non-Renewable Resource: Fossil fuels are finite resources that were formed over millions of years. They are being consumed at a much faster rate than they can be naturally replenished, meaning they will eventually run out.

Solution: We are actively seeking alternate sources of energy primarily because the traditional sources, fossil fuels (like coal, petroleum, and natural gas), are non-renewable. This means they exist in limited quantities on Earth and cannot be regenerated quickly once depleted. Fossil fuels are being consumed at an extremely high rate due to increasing global energy demands. If this trend continues, these vital resources will eventually be exhausted, leading to severe energy crises. Therefore, exploring and developing renewable and sustainable energy sources is crucial for meeting future energy needs without depleting natural reserves or causing excessive environmental damage.

Solution: The traditional methods of harnessing wind and water energy have been significantly modernized to meet our current energy demands more efficiently:

Water Energy: Traditionally, flowing water was used for simple tasks like grinding grain. Now, large dams are constructed in hilly regions to store vast amounts of water at a significant height. This stored water's potential energy is converted into kinetic energy as it flows down through pipes. This high-speed water flow is used to rotate turbines connected to electric generators, producing electricity in hydropower plants.

Wind Energy: Historically, windmills were used for tasks like pumping water or grinding. Today, the principle remains similar, but the scale and efficiency have increased dramatically. Modern windmills, often grouped in wind farms, have large blades designed to capture maximum wind energy. The rotational motion of these blades is used to turn the turbines of powerful electric generators, thus producing electricity on a large scale.