Science Lesson 7. PDF

## Energy in Daily Life ### Introduction - The image shows different types of work done in our daily life using various sources of energy. - The main source of energy for pulling water using a water pump is **electricity**. - The source of energy for humans and oxens to plough the field is **food...

## Energy in Daily Life ### Introduction - The image shows different types of work done in our daily life using various sources of energy. - The main source of energy for pulling water using a water pump is **electricity**. - The source of energy for humans and oxens to plough the field is **food** which provides **muscular energy**. ### Types of Energy - Heat, light, chemical, potential, muscular, etc. - Sources of energy: Sun, firewood, food, electric cells, electric generators, fossil fuels, etc. ### Non-renewable Sources of Energy - Found in nature over a long period, can't be replaced after usage. - Examples: Fossil fuels (coal, natural gas, mineral oil) and nuclear energy. - These sources are stored for a long time. ### Renewable Sources of Energy - Can be replaced immediately when finished. - Examples: Hydropower, wind energy, solar energy, biomass energy, geothermal energy. - We should give more priority to using renewable sources of energy. ### Fossil Fuels - Fossil fuels are remnants of dead organisms that have been preserved beneath the earth for millions of years. - Examples: Wood, coal, LPG, etc. - Solar energy is a product of chemical reactions. ### Formation of Fossil Fuels - Dead organisms get covered with layers of sediments in oceans. - High pressure and temperature transform dead organisms into fossil fuels like coal and petroleum. ### Advantages of Fossil Fuels - Cheap sources of energy. - Large deposits are available worldwide. - Easy to transport. - Multipurpose usage. - Led to the invention of machinery to utilize energy efficiently. ### Disadvantages of Fossil Fuels - Non-renewable. - Causes air pollution. - Carbon dioxide is a by-product from burning fossil fuels that leads to global warming. ### Ways of Saving Energy - Using alternative sources of energy. - Avoiding unnecessary energy usage. - Using renewable sources of energy over non-renewable. - Promoting solar and wind energy. - Increasing awareness of energy conservation. - Setting up gobar gas plants, solar plants, and wind energy plants. ### Heat - Necessary form of energy for survival. - Used in cooking, maintaining body temperature, running engines, industrial processes, etc. - Source of heat: Sun, burning fuels (wood, kerosene, petrol, coal), friction, etc. ### Temperature - Degree of hotness or coldness of a body. - Measured by using a **thermometer**. - SI unit is **Joule**. ### Types of Thermometers - **Clinical thermometer:** Used to measure body temperature - **Laboratory thermometer:** Used to measure the temperature of liquids and other substances. - **Digital thermometer:** Advanced technology for measuring temperature accurately. ### Working Principle of a Laboratory Thermometer - Based on the thermal expansion of mercury. - When heated, mercury expands inside a capillary tube, indicating the temperature. ### Units of Temperature - Celsius (°C) - Fahrenheit (°F) - Kelvin (K) is the SI unit of temperature. ### Relationship between Temperature Scales - Formulas for converting between the three scales: - F = (9/5)C + 32 - K = C + 273 ### Sound - Produced by vibrating objects. - Sound waves are a form of energy transmitted through a medium like air, water, or solid. - Sound cannot travel through a vacuum. ### Propagation of Sound - Sound waves travel in the form of **longitudinal** waves, which are characterized by compressions and rarefactions. - Sound waves travel faster through solids than liquids or gases. ### Types of Waves - **Longitudinal waves:** Particles in the medium vibrate parallel to the direction of the wave's propagation. - **Transverse waves:** Particles in the medium vibrate perpendicular to the direction of the wave's propagation. - Examples of longitudinal waves: Sound waves, compression waves in a spring. - Examples of transverse waves: Ripples on water, waves in a stretched string, light waves. ### Measuring Sound - **Amplitude:** Maximum displacement of a particle from its mean position. - **Time period:** Time taken for one complete cycle of a wave. - **Wavelength:** Distance between two successive crests or troughs. - **Frequency:** Number of complete waves passing a point in one second. - **Velocity:** Speed at which a wave travels. ### Relationship Between Wavelength and Frequency - The velocity of a wave is the product of its frequency and wavelength: - v = f x λ ### Loudness of Sound - The loudness of a sound depends on its amplitude. - The higher the amplitude, the louder the sound. ### Measuring Loudness - The SI unit for measuring the loudness of sound is **decibels (dB)**.