Physics in Energy Conventional Energy

Energy ka concept physics ka core hai. Conventional energy sources—fossil fuels (coal, oil, natural gas) aur nuclear energy—humari daily life aur industry me bohot essential hain. Ye energy sources thermodynamics, mechanics, nuclear physics, and electromagnetism ke principles par operate karte hain. Is post me hum explore karenge kaise physics principles conventional energy systems me kaam karte hain, unka conversion process, efficiency, aur real-world applications.

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1. Introduction

Conventional Energy Sources:

• Fossil fuels: Coal, oil, natural gas
• Nuclear energy: Fission-based power generation

Physics Importance:

1. Energy conversion from chemical/nuclear to mechanical/electric
2. Thermodynamic cycles in engines and turbines
3. Efficiency and losses via heat, friction, and resistance
4. Electrical energy generation and transmission

Key Physical Quantities:

• Energy (E) – Joules
• Power (P) – Watts
• Work (W) – Joules
• Temperature (T) – Kelvin
• Pressure (P) – Pascal
• Efficiency (η) – %

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2. Fossil Fuels and Energy Conversion

2.1 Chemical Energy in Fossil Fuels

• Fossil fuels contain stored chemical energy from ancient organic matter
• Combustion reaction releases energy:

CxHy+O2→CO2+H2O+Heat\text{C}_x\text{H}_y + O_2 \rightarrow CO_2 + H_2O + \text{Heat}Cx​Hy​+O2​→CO2​+H2​O+Heat

Physics Concepts:

• Heat energy → kinetic energy of molecules
• Conservation of energy

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2.2 Thermodynamics of Combustion

• First Law of Thermodynamics:

ΔU=Q−W\Delta U = Q – WΔU=Q−W

Where ΔU = change in internal energy, Q = heat added, W = work done

• Heat energy released by combustion used to generate steam or hot gases

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2.3 Heat Engines

• Fossil fuel power plants use steam turbines
• Thermodynamic cycle: Rankine Cycle
  1. Boiler: Heat added to water → steam
  2. Turbine: Steam expands → does mechanical work
  3. Condenser: Steam condensed → water
  4. Pump: Water sent back to boiler

Efficiency of heat engine: η=WoutQin×100%\eta = \frac{W_{\text{out}}}{Q_{\text{in}}} \times 100\%η=Qin​Wout​​×100%

• Typical thermal efficiency: 30–40%

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2.4 Examples of Fossil Fuel Power Plants

• Coal-fired plant: Converts chemical energy → thermal energy → mechanical energy → electrical energy
• Natural gas plant: Gas turbines, Brayton cycle
• Oil-fired plants: Similar to coal plants but faster startup

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3. Electrical Energy Generation

3.1 Electromagnetic Induction

• Faraday’s law: Changing magnetic flux induces emf

E=−dΦBdt\mathcal{E} = -\frac{d\Phi_B}{dt}E=−dtdΦB​​

• Turbines rotate coils in magnetic field → electricity generated

3.2 Generators

• Mechanical energy from steam turbines → rotational motion → electrical energy
• Physics: Lorentz force, motion of charges in magnetic field

F=q(v×B)\mathbf{F} = q (\mathbf{v} \times \mathbf{B})F=q(v×B)

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4. Efficiency and Energy Losses

4.1 Thermal Efficiency

• Ratio of useful work to heat energy input
• Losses: Heat in flue gases, friction, vibration

4.2 Electrical Efficiency

• Power loss in transmission lines:

Ploss=I2RP_{\text{loss}} = I^2 RPloss​=I2R

• High-voltage transmission reduces I → reduces losses

4.3 Carnot Efficiency

• Maximum possible efficiency depends on temperature difference:

ηmax=1−TCTH\eta_{\text{max}} = 1 – \frac{T_C}{T_H}ηmax​=1−TH​TC​​

Where TH = boiler temp, TC = condenser temp

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5. Nuclear Energy

5.1 Nuclear Fission

• Nucleus splits → releases energy

235U+n→236U∗→Ba+Kr+3n+Energy^{235}U + n \rightarrow ^{236}U^* \rightarrow Ba + Kr + 3n + \text{Energy}235U+n→236U∗→Ba+Kr+3n+Energy

• Energy per fission ~ 200 MeV (~3.2 × 10⁻¹¹ J)

Physics Concepts:

• Mass-energy equivalence:

E=Δmc2E = \Delta m c^2E=Δmc2

• Chain reaction controlled via moderators and control rods

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5.2 Nuclear Power Plants

1. Reactor core: Fission releases heat
2. Heat → steam → turbine → generator → electricity
3. Condenser → water recycled

Efficiency: Thermal efficiency ~33–37%

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5.3 Advantages and Disadvantages

Advantages:

• High energy density
• Low greenhouse emissions

Disadvantages:

• Radioactive waste
• High initial setup cost
• Safety concerns

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6. Mechanical Energy Conversion

• Steam turbines: Thermal → mechanical → electrical
• Gas turbines: Combustion gases expand → mechanical work
• Physics: Conservation of energy, Newton’s laws, rotational dynamics

Example: Torque on turbine shaft: τ=r×F\tau = r \times Fτ=r×F

• Rotational kinetic energy:

Ek=12Iω2E_k = \frac{1}{2} I \omega^2Ek​=21​Iω2

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7. Fluid Mechanics in Power Plants

• Steam and combustion gases are fluids
• Principles applied:
  • Bernoulli’s equation for flow velocity and pressure

P+12ρv2+ρgh=constantP + \frac{1}{2}\rho v^2 + \rho g h = \text{constant}P+21​ρv2+ρgh=constant

• Turbine blade design for maximum efficiency
• Physics ensures optimal conversion of thermal energy to mechanical energy

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8. Heat Transfer in Conventional Energy Systems

1. Conduction: Through turbine blades, boiler walls
2. Convection: Circulation of water/steam
3. Radiation: Heat loss to environment

Design goal: Minimize losses, maximize useful work

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9. Environmental Physics Considerations

• Combustion → CO2, NOx emissions → greenhouse effect
• Physics of pollutant dispersion: Wind patterns, diffusion, turbulence
• Cooling towers: Evaporative cooling, heat dissipation

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10. Numerical Examples

Example 1: Thermal Efficiency

• Steam plant: Heat input Q_in = 5 × 10⁶ J, Work output W = 1.5 × 10⁶ J

η=WQin×100%=1.5×1065×106×100%=30%\eta = \frac{W}{Q_{in}} \times 100\% = \frac{1.5 \times 10^6}{5 \times 10^6} \times 100\% = 30\%η=Qin​W​×100%=5×1061.5×106​×100%=30%

Example 2: Energy from Fission

• 1 mole U-235 (~6.022 × 10²³ nuclei), energy per fission = 200 MeV

Etotal=6.022×1023×200×106×1.6×10−19≈1.93×1013 JE_{\text{total}} = 6.022 \times 10^{23} \times 200 \times 10^6 \times 1.6 \times 10^{-19} \approx 1.93 \times 10^{13} \, JEtotal​=6.022×1023×200×106×1.6×10−19≈1.93×1013J

Example 3: Power Loss in Transmission

• I = 500 A, R = 0.2 Ω

Ploss=I2R=5002×0.2=50,000 WP_{loss} = I^2 R = 500^2 \times 0.2 = 50,000 \, WPloss​=I2R=5002×0.2=50,000W

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11. Summary Table

Energy Source	Physics Principle	Conversion Process	Efficiency
Coal	Combustion, thermodynamics	Chemical → Heat → Mechanical → Electrical	30–40%
Oil	Combustion, fluid dynamics	Chemical → Thermal → Mechanical → Electrical	30–40%
Natural Gas	Combustion, Brayton cycle	Chemical → Thermal → Mechanical → Electrical	35–40%
Nuclear (U-235)	Fission, mass-energy equivalence	Nuclear → Thermal → Mechanical → Electrical	33–37%
Steam Turbine	Thermodynamics, mechanics	Heat → Rotational kinetic energy → Electricity	30–40%
Generator	Electromagnetic induction	Mechanical → Electrical energy	90–95%