Sources of Energy — Karnataka (SSLC) Class 10 Science Solutions (Free)

Conventional (finite, polluting): Coal, petroleum, natural gas, nuclear fuel. Non-conventional (renewable, clean): Solar (sunlight), wind, hydroelectric (falling water), biomass (plant waste), geothermal (Earth's heat), tidal (ocean). Conventional sources depleting; non-conventional sustainable for future.

Coal burned to heat water → steam at high pressure → steam rotates turbine (mechanical energy) → turbine shaft rotates generator coil in magnetic field → electricity generated. Condenser cools steam back to water (recycled). Cooling towers release waste heat. Efficiency ≈ 40%; rest is waste heat to environment.

Dam built across river to create reservoir. Water stored at height has gravitational potential energy. Water released through penstock (pipe) falls under gravity, rotating turbines. Turbines drive generators to produce electricity. Advantages: renewable, no pollution, long lifespan. Disadvantages: high initial cost, ecosystem impact, displacement of people.

Solar cell made of semiconductor (silicon); junction between p-type and n-type layers. Photons from sunlight excite electrons, creating electron-hole pairs. Electric field at junction separates them, driving current through external circuit. EMF produced ≈ 0.6 V per cell; cells connected in series/parallel for higher voltage/current.

Advantages: (1) Enormous energy from small mass (E = mc²), (2) No CO₂ emissions, (3) Compact, high efficiency. Disadvantages: (1) Radioactive waste disposal problem, (2) Risk of accidents (meltdown), (3) High construction cost, (4) Security concerns, (5) Public fear. Nuclear fission splits atoms; fusion combines them (future promise).

Wind energy: kinetic energy of moving air. Wind turbine: large blades catch wind, rotating shaft drives generator. Requires minimum wind speed ≈ 3 m/s, optimal ≈ 10–15 m/s. Advantages: renewable, no emissions, minimal land use (under turbines can farm). Disadvantages: depends on weather, noise, visual impact, bird deaths.

Biomass: organic matter (wood, agricultural waste, dung, sugar residue). Energy extraction methods: (1) Direct burning → heat/steam, (2) Biogas fermentation (anaerobic) → methane gas, (3) Biofuel production (ethanol from sugarcane). Advantages: renewable, reduces waste, carbon neutral (CO₂ absorbed by crops). Disadvantages: lower efficiency than fossil fuels, requires large land area.