Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Mechanics → Work, Energy and Power ↓


Power and efficiency


Understanding power

In physics, the term "power" means the rate at which work is done or energy is transferred or transformed. It is a measure of how quickly something happens or how much energy is used in a period of time. The concept of power is quite intuitive when you think about everyday experiences, such as how quickly you can climb stairs or how quickly a car accelerates.

Definition and formula

Power is calculated using the following formula:

P = (frac{W}{t})

Where P is power, W is the work done, and t is the time taken to do the work.

In the International System of Units (SI), power is measured in watts (W), where one watt is equal to one joule per second. It is written as:

1 W = 1 J/s

Visualizing power with an example

Let's consider a simple example: lifting a weight. Imagine you have a 10 kg weight, and you lift it 2 meters above the ground in 4 seconds. We want to calculate how much power you used to lift the weight.

First, calculate the work done:

Work done (W) = Force × Distance = (Mass × Gravity) × Height = 10 kg × 9.8 m/s² × 2 m = 196 Joules

Now, calculate the power using the power formula:

Power (P) = (frac{W}{t}) = (frac{196 J}{4 s}) = 49 W

This means you used 49 watts of power to lift the weight.

10 Kg 2 m

Description of efficiency

Efficiency is another important concept in the field of physics, especially when discussing machines or systems. It refers to the effectiveness of a machine or process in converting input energy into useful output energy. Not all the energy put into a machine is used to perform useful work, as some of it is lost to the environment, mainly as heat due to friction or other factors.

Definition and formula

The efficiency can be calculated using the following formula:

[text{Efficiency} (%) = left(frac{text{Useful Output Energy}}{text{Input Energy}}right) times 100]

Efficiency is expressed as a percentage, with a higher percentage indicating a more efficient process or machine.

Understanding efficiency through an example

Consider a car engine that converts chemical energy from the fuel into mechanical energy to drive the car. However, not all the energy from the fuel is converted into motion; some energy is lost as heat and sound.

Suppose the engine has an input energy of 1000 joules and provides useful output energy of 250 joules to drive the car. The efficiency of the engine will be calculated as:

Efficiency = (left(frac{250 J}{1000 J}right) times 100) = 25%

This means that only 25% of the fuel energy is used to run the car, while the remaining energy is wasted.

Input Energy Useful Output Loss of energy

Real-life examples of power and efficiency

Example 1: Home Appliances

Household appliances are a common place to see the concepts of power and efficiency at work. For example, consider a 60-watt light bulb. This means the bulb uses 60 joules of electrical energy every second to produce light and heat. When shopping for appliances, you may see an energy rating that indicates how efficient the appliance is in terms of energy use.

Example 2: Automobile

Cars offer a classic example of power and efficiency. A car's engine power is often measured in horsepower or kilowatts. Car fuel efficiency is an important factor for many buyers, usually expressed in miles per gallon (mpg) or kilometers per liter (km/L). A more efficient car can travel a greater distance using the same amount of fuel.

Example 3: Power plant

Power plants generate electricity that is distributed to homes and industries. The efficiency of a power plant is important because it affects how much fuel is needed to generate electricity. Improving efficiency at power plants can significantly reduce fuel consumption and lead to considerable economic and environmental benefits.

Energy-efficient practices and technologies are constantly being developed to reduce losses and increase the work output from a given input energy. From more efficient engines and motors to better heating and cooling systems, understanding and applying the principles of energy and efficiency plays a key role in conservation efforts and innovation.

Conclusion

In short, power and efficiency are essential concepts in physics that relate to the rate of work done and the effectiveness of energy conversion, respectively. Understanding these concepts allows us to analyze and improve the performance and energy use of various systems and devices, leading to significant impacts both in everyday life and on a larger scale, such as industrial operations and environmental management.


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Power and efficiency

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