Physics

• Heat 


  Heat is the internal energy of molecules constituting the body. It flows from a hot body to a cold body when they are kept in contact.
• Calorie

  One calorie is the quantity of heat energy required to raise the temperature of 1 g of water from 14.5°C to 15.5°C.
• Temperature 


  Temperature is a parameter which tells the thermal state of a body (i.e., the degree of hotness or coldness of body). It determines the direction of flow of heat when two bodies at different temperatures are placed in contact.
• calorimetry


  The measurement of quantity of heat is known as calorimetry
• Heat capacity 


  The term heat capacity of a body is the amount of heat energy required to raise it's temperature by 1° C (or 1 K).
• Specific heat capacity 


  The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of unit mass of that substance through 1°C (or 1 K).
• Name two factors on which the heat energy librated by a body on cooling depends.

  The factors on which the heat energy liberated by a body on cooling depends are: Mass of the body Temperature of the body
• What is the principle of method of mixture ? What other name is given to it? Name the law on which this principle is based


  Heat energy lost by the hot body = Heat energy gained by the cold body. This is called the principle of method of mixture. The other name given to it is the principle of calorimetry. This principle is based on the law of conservation of energy.
• Why do the farmers fill their fields with water on a cold winter night

  On a cold winter night, if the atmospheric temperature falls below 0° C, water in the fine capillaries of plants will freeze, so the veins will burst due to the increase in volume of water on freezing. As a result, plants will die and the crop will get destroyed. In order to save crop on such cold nights, farmers fill their fields with water because water has a high specific heat capacity, so it does not allow the temperature in the surrounding area of plants to fall up to 0° C.
• Discuss the role of high specific heat capacity of water with reference to climate in coastal areas

  The specific heat capacity of water is very high. It is about five times as high as that of sand. Hence, the heat energy required for the same rise in temperature by a certain mass of water will be nearly five times than that required by the same mass of sand. Similarly, a certain mass of water will impart nearly five times more heat energy than that given by the same mass of sand for the same fall in temperature.
• Water is used in hot water bottles for fomentation. Give reason.


  Hot water bottles are used for fomentation because water does not cool quickly due to it's high specific heat capacity, so a hot water bottle provides more heat energy for fomentation over a longer period. Hence, water is used in hot water bottles for fomentation.
• What property of water makes it an effective coolant

  Water is an effective coolant. By allowing water to flow in pipes around the heated parts of a machine, heat energy from such parts is removed. Water in pipes can extract more heat from the surroundings without much rise in it's temperature because of it's high specific heat capacity. This is why radiators in car and generator use water for cooling.
• Radiators in cars and generators use water for cooling.
• Water in a car radiator can absorb more heat without much rise in temperature due to its high specific heat capacity, acting as an effective coolant.
• In cold countries, water is used as a heat reservoir for wine and juice bottles to avoid their freezing.
• Water due to its high specific heat capacity can impart a large amount of heat before reaching its freezing point, acting as an effective heat reservoir.
• Bottles kept in water remain warm and do not freeze when there is a considerable fall in temperature.
• Renewable energy

  A natural source providing us with energy continuously
• Main sources of renewable energy

  Sun, Wind, Flowing water, Biomass and biofuels from waste, tides
• Solar energy


  The energy radiated out by sun.
• wind

  The kinetic energy of wind
• Hydro energy


  the kinetic energy possessed by flowing water
• Bioenergy


  the chemical energy stored in the biomass
• Tidal energy


  the energy possessed by rising and falling water in tides
• Ocean thermal energy 


  The energy available due to the difference in temperature of water at the surface and at deeper levels of ocean.
• Oceanic (or sea) waves energy


   the kinetic energy possessed by fast-moving oceanic (or sea) waves.
• Geo thermal energy 


  The heat energy possessed by rocks inside the earth is called geothermal energy.