Sources of Energy – Case-based Questions with Answers
Physics — Chapter 15: Sources of Energy
20 Case-Based Questions & Answers — NCERT-aligned for CBSE Class 10 board exam preparation. Each case includes short, clear questions and exam-oriented answers.
- Interpret real‑life energy scenarios and identify energy sources used.
- Discuss advantages, limitations and environmental impacts concisely.
- Apply concepts of energy conversion, conservation and storage to practical cases.
- Use NCERT principles to explain and evaluate solutions.
20 Case-Based Questions (Topic-wise)
Case 1 — Village Energy Use
In a small village many houses use firewood for cooking and a few have LPG connection. The school roof has space for solar panels.
Q1. Identify commercial and non‑commercial energy sources in this case.
Answer: LPG is a commercial energy source (bought in the market). Firewood is a non‑commercial source (locally collected, not traded).
Q2. Suggest two benefits of installing rooftop solar at the school.
Answer: (1) Provides clean, low‑cost electricity for lighting and fans, reducing dependence on grid or diesel. (2) Educational value—students learn about renewables; potential to power evening study programs.
Case 2 — City Commuters
A city promotes electric buses and charging stations, while many personal vehicles still use petrol and diesel.
Q3. Explain how electric buses can reduce urban pollution compared to diesel buses.
Answer: Electric buses produce zero tailpipe emissions, reducing NOx, SOx and particulate pollution; if charged from clean electricity (solar, wind), overall greenhouse gas emissions decrease versus diesel buses.
Q4. What infrastructure is essential to support a shift to electric buses?
Answer: Reliable charging stations, grid upgrades to handle load, battery maintenance facilities and planning for fast chargers at depots and major stops.
Case 3 — Rural Biogas Initiative
A cooperative installs biogas plants using cattle dung; the slurry is used as fertiliser in fields.
Q5. Describe two benefits of this biogas project.
Answer: (1) Provides clean cooking fuel, reducing indoor air pollution from firewood. (2) Produces organic fertiliser (slurry) improving soil fertility and reducing chemical fertiliser use.
Q6. State one operational challenge and a solution.
Answer: Challenge: Regular feedstock supply and maintenance. Solution: Community management, scheduled feeding and training for local operators to ensure plant upkeep.
Case 4 — Coastal Wind Farm Proposal
A developer plans a wind farm along the coast where wind speeds are high but seabirds are present.
Q7. List two advantages and one environmental concern of the wind farm.
Answer: Advantages: (1) High energy yield due to strong coastal winds; (2) Low operational emissions. Concern: Potential harm to seabirds and disruption of marine ecosystems if not properly sited.
Q8. Suggest a mitigation measure for the environmental concern.
Answer: Conduct environmental impact assessment (EIA), adjust turbine placement to avoid bird migration routes, and use monitoring to modify operations during high migration periods.
Case 5 — Thermal Power Plant Expansion
A region proposes expanding a coal‑fired power plant to meet rising demand.
Q9. Identify two environmental problems associated with coal plants.
Answer: (1) High CO₂ emissions contributing to climate change; (2) Air pollutants (SO₂, NOx, particulates) causing health problems and acid rain; coal ash disposal issues also pose contamination risks.
Q10. Recommend two strategies to reduce environmental impact while meeting energy needs.
Answer: (1) Improve plant efficiency (supercritical boilers) and install flue gas cleaning (desulphurisation, particulate filters); (2) Complement with renewables (solar/wind) and demand‑side measures to reduce additional coal dependence.
Case 6 — Oil Spill Near Coast
An accidental oil spill from a tanker affects a coastal community and fisheries.
Q11. Explain immediate environmental hazards of oil spills.
Answer: Oil coats marine organisms, reduces oxygen exchange, harms birds and fish, contaminates shorelines and disrupts food chains and livelihoods (fisheries).
Q12. Suggest two short-term cleanup or mitigation measures.
Answer">Answer: Use booms and skimmers to contain and remove oil; apply shoreline cleanup and wildlife rescue operations; deploy dispersants cautiously if appropriate and monitor ecological effects.
Case 7 — Urban Air Quality Monitoring
A city shows rising particulate levels; data links peaks to power plant emissions and vehicle traffic.
Q13. Recommend two policies to reduce particulate pollution.
Answer: (1) Promote clean fuels and upgrade emission standards for vehicles; (2) Tighten emission controls on industries and power plants (electrostatic precipitators, low‑sulfur fuels) and incentivise public transport.
Q14. How can energy conservation help improve air quality?
Answer: Conservation reduces demand for electricity and transport fuel, thereby lowering combustion emissions from power plants and vehicles; measures include efficiency standards, public awareness and reduced peak loads that often require dirtier sources.
Case 8 — Methane Leak from Pipeline
A natural gas pipeline leak was detected near a residential area.
Q15. Why are methane leaks a concern environmentally?
Answer: Methane is a potent greenhouse gas with a much higher global warming potential than CO₂ over short timescales; leaks increase atmospheric warming and contribute to climate change.
Q16. State an immediate safety action and a long-term preventive measure.
Answer: Immediate: Evacuate and shut off gas flow, repair the leak. Long‑term: Regular pipeline maintenance, leak detection systems and replacing aging infrastructure to minimise future leaks.
Case 9 — Coal Ash Pond Failure
A coal ash pond breach contaminates nearby groundwater used for irrigation.
Q17. What are the likely contaminants from coal ash and their risks?
Answer: Heavy metals (arsenic, lead, mercury) and soluble salts can leach into groundwater causing toxicity to crops and health risks if consumed; bioaccumulation in food chains is a concern.
Q18. Outline two remediation steps the local authority should take.
Answer">Answer: Stop further leaching by containing/removing ash, provide alternative safe water sources, and remediate contaminated soil/water through filtration, phytoremediation or engineered treatment systems while monitoring health impacts.
Case 10 — Village Microgrid
A remote village installs a microgrid combining solar panels, a small hydro generator and battery storage to supply evening lighting and a clinic.
Q19. Explain why combining different renewables is beneficial for reliability.
Answer: Different resources complement each other (solar generation during day, hydro can supply at night/seasonally); storage buffers variability, reducing blackout risk and improving supply stability.
Q20. Suggest two maintenance practices to keep the microgrid reliable.
Answer">Answer: Regular battery health checks and inverter servicing; periodic cleaning and inspection of panels/turbines and local operator training to handle minor faults promptly.
Case 11 — Large PV Farm & Grid Constraints
A new solar farm expects to export large power volumes to the grid, but the local grid has limited capacity.
Q21. What short-term and long-term measures can help integrate the farm?
Answer: Short‑term: Use in‑situ storage (batteries) and curtailment agreements during peak export; Long‑term: Upgrade grid infrastructure, add transmission lines and implement smart grid management and demand response programs.
Q22. How does energy storage improve grid integration for intermittent renewables?
Answer">Answer: Storage absorbs excess generation and supplies during low production, smoothing output, providing frequency regulation and reducing the need for fossil backup generation.
Case 12 — School Energy Audit
A school conducts an energy audit and finds most energy used for lighting and fans; they consider LEDs and a small rooftop solar installer.
Q23. Estimate two quick wins to reduce the school's energy use.
Answer: Replace incandescent/fluorescent lights with LED fixtures and install ceiling fans with efficient motors; add motion sensors in low‑use areas to prevent unnecessary lighting.
Q24. Explain how the school can finance a rooftop system with limited funds.
Answer">Answer: Use government subsidies or school‑specific solar schemes, explore third‑party ownership (solar‑as‑a‑service) or crowd‑funding/local CSR partnerships to cover upfront costs while benefiting from reduced electricity bills.
Case 13 — Offshore Wind & Fisheries
A coastal community raises concerns that proposed offshore wind turbines could affect fish catch and local livelihoods.
Q25. How can planners address the community's concerns?
Answer: Conduct participatory consultations, schedule studies on marine ecology and fisheries, design turbine layout to minimise disruption, provide compensation or alternative livelihoods and consider co‑existence measures (no‑fishing zones with monitoring).
Q26. Give one example where offshore wind co‑exists with other marine activities.
Case 14 — Proposed Nuclear Plant Near City
A government proposes a nuclear power plant to provide baseload power for a growing city; residents raise safety and waste concerns.
Q27. Provide two arguments in favour of the plant and two concerns residents may have.
Answer: In favour: (1) Nuclear provides large amounts of reliable, low‑carbon baseload electricity; (2) Reduces dependence on imported fossil fuels. Concerns: (1) Risk of accidents and radiation exposure; (2) Long‑term management of radioactive waste and public apprehension about storage safety.
Q28. What measures can authorities take to increase public trust?
Answer">Answer: Transparent communication about safety systems, independent environmental and safety assessments, robust emergency preparedness plans, community benefits, and clear radioactive waste management strategies with secure storage and monitoring.
Case 15 — Battery Recycling Initiative
With more solar batteries installed, a town sets up a collection and recycling program for end‑of‑life lithium batteries.
Q29. Why is battery recycling important?
Answer: Recycling recovers valuable materials, reduces environmental contamination from heavy metals, decreases demand for raw mining and supports circular economy principles for sustainable energy systems.
Q30. Suggest two elements of an effective local recycling program.
Answer">Answer: Safe collection points and transport logistics, partnerships with certified recyclers, public awareness campaigns and incentives for returning old batteries to encourage participation.
Case 16 — Peak Demand and Load Shedding
A region experiences summer peaks and occasional load shedding; policymakers consider demand response and rooftop solar as options.
Q31. How can rooftop solar help reduce peak demand?
Answer: Rooftop solar generates most during daytime peak periods (especially in summer), reducing net load on the grid and thereby lowering peak demand; combined with storage it can supply evening peaks as well.
Q32. Explain what demand response is and how it can reduce load shedding.
Answer">Answer: Demand response incentivises consumers to shift or reduce consumption during peak times (e.g., through time‑of‑use tariffs or automated controls), flattening demand peaks and reducing the need to shed load or start expensive peaking plants.
Case 17 — School Energy Awareness Campaign
A school wants to run campaigns to teach students energy saving habits.
Q33. List three simple behaviours to promote among students to conserve energy.
Answer: (1) Switch off lights and fans when leaving rooms; (2) Charge devices only when necessary and avoid overnight charging; (3) Use natural daylight during daytime classes.
Q34. How can practical projects reinforce learning?
Answer}>Answer: Hands‑on projects like building solar lamps, measuring energy use for different bulbs, or a biogas model let students apply concepts, improving retention and inspiring sustainable choices.
Case 18 — Farmer Using Diesel Pump vs Solar Pump
A farmer currently uses a diesel water pump and considers replacing it with a solar‑powered pump.
Q35. Compare operating costs and environmental impact of the two options.
Answer: Diesel pumps have lower upfront cost but higher fuel and maintenance costs and emit CO₂ and particulates; solar pumps have higher initial cost but near‑zero fuel cost and lower emissions, providing long‑term savings and cleaner operations.
Q36. Suggest two factors the farmer should consider before switching.
Answer}>Answer: (1) Water demand pattern and pump sizing to ensure solar capacity meets irrigation needs; (2) Availability of subsidies, financing options and maintenance support for panels and inverters.
Case 19 — Coastal City Considering Tidal Energy
The city explores tidal barrage options but worries about coastal ecosystem impacts and navigation.
Q37. What makes tidal energy attractive despite its constraints?
Answer: Tidal energy is predictable and reliable (based on lunar cycles) and can provide consistent power with low operating emissions—valuable for baseload in suitable locations.
Q38. Recommend one preliminary study the city should commission.
Answer}>Answer: A comprehensive environmental impact assessment (EIA) including tidal modelling, marine ecology surveys and navigation impact analysis to assess feasibility and mitigation options.
Case 20 — Community Solar with Net Metering
A housing society installs community solar on shared rooftop and plans to use net metering to distribute credits.
Q39. Explain how net metering will benefit society members.
Answer: Net metering credits excess generation to members’ electricity accounts, reducing monthly bills and improving solar ROI by offsetting energy consumed from the grid when solar output is low.
Q40. Suggest two governance measures to ensure fair distribution of benefits.
Answer: (1) Maintain transparent accounting of generation and individual consumption, with a fair credit allocation formula; (2) Create a management committee to handle maintenance, billing disputes and reinvestment of savings for shared benefits.