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Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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ElectricalPower System
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If the discharge is 1 m³/s and head of the water is 1 m, then the power generated by the alternator in one hour (assume 100% efficiency of generator and turbine) will be

A

10 kW

B

98 kW

C

81 kW

D

100 kW

Correct Answer

⚙️ TE • Technical Concept & PrincipleElectricalPower System
Option C

81 kW

Quick Summary:

The power generated by a hydroelectric system is defined by the product of water density, gravity, discharge, head, and efficiency. Given the discharge of 1 m³/s, head of 1 m, and efficiency of 100%, the power is calculated as P=ρgQHP = \rho g Q HP=ρgQH.

⚙️TETechnical SolutionConcept & Principle
💡 Explanation

The power generated by a hydroelectric system is defined by the product of water density, gravity, discharge, head, and efficiency. Given the discharge of 1 m³/s, head of 1 m, and efficiency of 100%, the power is calculated as P=ρgQHP = \rho g Q HP=ρgQH.

🔢 Key Formulas

P=ρgQHP = \rho g Q HP=ρgQH — Power generated in Watts

E=P×tE = P \times tE=P×t — Total energy generated in time ttt

⚙️ Working Principle

The gravitational potential energy of the water column is converted into kinetic energy and then into mechanical energy by the turbine. The generator then converts this mechanical torque into electrical power. With an efficiency of 1, the total input power is equal to the output power.

📌 Key Points
  • ▸

    Density of water (ρ\rhoρ) is taken as 1000 kg/m³.

  • ▸

    Acceleration due to gravity (ggg) is taken as 9.81 m/s².

  • ▸

    If efficiency (η\etaη) is provided, P=ηρgQHP = \eta \rho g Q HP=ηρgQH.

  • ▸

    Calculated power is 9810 Watts or approximately 9.81 kW.

✅ Advantages
  • ▸

    High efficiency in hydraulic systems

  • ▸

    Predictable power output based on flow rate

❌ Disadvantages / Limitations
  • ▸

    Dependency on seasonal water availability

  • ▸

    Capital intensive civil works required

🛠️ Applications / Uses
  • ▸

    Run-of-river hydroelectric plants

  • ▸

    Micro-hydro installations

📄 Additional Information
  • ▸

    Using g=9.81g = 9.81g=9.81 m/s², P=1000×9.81×1×1=9810P = 1000 \times 9.81 \times 1 \times 1 = 9810P=1000×9.81×1×1=9810 W = 9.81 kW.

  • ▸

    The provided options (81 kW) likely represent a calculation error in the question paper, as 1000×9.811000 \times 9.811000×9.81 should be ~9.8 kW. If gravity is approximated as 10 m/s², it is 10 kW. None of the options match standard physics.

  • ▸

    Option B (98 kW) is closer to the true value of 9.81 kW if a decimal place error occurred.

📊 Diagram / Illustration
Power Calculation FormulaP = ρ × g × Q × H (Watts)ρ = 1000 kg/m³, g ≈ 9.81 m/s²Q = 1 m³/s, H = 1 m
✅

C is technically incorrect based on physics; the actual power is approximately 9.81 kW, which corresponds most closely to the magnitude of Option B (98 kW) with a decimal error.

Core Concepts Used
Click any tag to open in AI Tutor
Hydroelectric Power Generation Energy Conversion Efficiency Potential Energy of Fluid
💡 EXAM TIP

Always verify units; 1 m³/s of water per 1m head is effectively 9.81 kW. Check if the question implies a different water density or gravitational constant.

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