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1. What is a good source of energy?
Answer:
A good source of energy has the following characteristics:
- Produces a large amount of work per unit volume or mass.
- Is easily accessible.
- Is easy to store and transport.
- Is economical.
2. What is a good fuel?
Answer:
A good fuel possesses these properties:
- Cost-effective and affordable.
- Readily available.
- Ignition temperature well above normal ambient conditions.
- Convenient to handle and transport.
- Does not produce poisonous materials during combustion.
- Has a steady and controllable combustion rate.
- Leaves no residue or ash after burning.
- High calorific value to produce significant heat with minimal fuel.
3. If you could use any source of energy for heating your food, which one would you use and why?
Answer:
I would choose LPG (liquefied petroleum gas) for heating food because:
- It has a suitable ignition temperature, ensuring safe operation.
- It offers a high calorific value, producing efficient heat.
- It is non-polluting, burning cleanly with minimal harmful emissions.
4. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:
Two renewable energy sources are:
- Biomass energy: Renewable because waste products are continuously generated, and plants/trees are regularly regrown, ensuring a sustainable supply.
- Hydropower, wind, solar, or ocean energy: Renewable as these sources can be harnessed as long as the solar system exists, providing a consistent and inexhaustible supply.
5. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
Two exhaustible energy sources are:
- Coal: Exhaustible because its reserves are limited and estimated to last about 200 years, while it takes millions of years to form.
- Petroleum: Exhaustible due to finite reserves that may be depleted in approximately 200 years, with formation requiring millions of years.
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1. What are the disadvantages of fossil fuels?
Answer:
The disadvantages of fossil fuels include:
- Produce large amounts of carbon dioxide, contributing to the greenhouse effect.
- Burning (e.g., coal) generates smoke, causing air pollution.
- Emit acidic gases (sulphur dioxide, nitrogen oxides), leading to acid rain that harms water and soil resources.
- Non-renewable, as they take millions of years to form and cannot be replenished quickly.
2. Why are we looking at alternate sources of energy?
Answer:
We seek alternate energy sources because:
- Fossil fuels and nuclear fuels are limited and may be depleted soon.
- Burning fossil fuels causes pollution, and nuclear power plants produce radioactive waste, both threatening the environment.
3. How has the traditional use of wind and water energy been modified for convenience?
Answer:
Traditional uses of wind and water energy have been modernized as follows:
- Wind energy: Windmill farms are established to generate electricity efficiently.
- Water energy: Hydro-power plants harness the energy of falling or flowing water using turbines to drive generators, producing electricity.
Page 253
1. What kind of mirror—concave, convex, or plane—would be best suited for use in a solar cooker? Why?
Answer:
A concave mirror is best suited for a solar cooker because:
- It focuses sunlight into a small area, creating a high temperature sufficient for cooking.
2. What are the limitations of the energy that can be obtained from the oceans?
Answer:
Ocean energy can be obtained as tidal energy, wave energy, and ocean thermal energy. Their limitations are:
- Tidal Energy:
- Limited suitable sites for building tidal dams.
- Insufficient rise and fall of seawater during tides to generate large-scale electricity.
- Wave Energy:
- Few locations where waves strike shorelines with sufficient power for energy generation.
- Ocean Thermal Energy:
- Requires a temperature difference of at least 20°C between surface and deeper ocean water, involving high operational costs.
3. What is geothermal energy?
Answer:
Geothermal energy is the heat stored in certain regions of the Earth, known as hot spots, where upward-moving magma collects due to geological changes. When underground water contacts these hot spots, steam is generated, which is used to produce electricity via pipes and turbines. Sometimes, hot water escapes to the surface as hot springs.
4. What are the advantages of nuclear energy?
Answer:
The advantages of nuclear energy include:
- Produces a large amount of energy from a small quantity of nuclear fuel (e.g., uranium-235).
- Once loaded, a nuclear power plant can generate electricity for 2–3 years without needing additional fuel.
- Does not emit carbon dioxide (greenhouse gas) or sulphur dioxide (acid rain contributor).
5. Can any source of energy be pollution-free? Why or why not?
Answer:
No source of energy is completely pollution-free because:
- Even clean energy sources may cause environmental damage during their assembly or infrastructure development.
6. Hydrogen has been used as rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer:
Hydrogen is a cleaner fuel than CNG because:
- Burning hydrogen produces only water, which is harmless.
- Burning CNG produces carbon dioxide, which contributes to the greenhouse effect and long-term environmental heating.