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प्रश्न
Explain, why does a wise farmer water his fields, if forecast is forst?
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उत्तर
The frost can seriously damage the leaves and fruit of plants. When a farmer waters his fields, during, night, this water gives large amount of heat energy, because 1 g of water will liberate 4.2 J of energy for every 1°C fall in temperature. Thus, the air around the field is saturated with heat energy and its temperature does not fall below 0°C. Thus, no frost is formed.
संबंधित प्रश्न
45 g of water at 50°C in a beaker is cooled when 50 g of copper at 18° C is added to it. The contents are stirred till a final constant temperature is reached. Calculate this final temperature. The specific heat capacity of copper is 0.39 J g-1K-1 and that of water is 4.2 J g-1K-1. State the assumption used.
Give three reasons for the increase of green house gases.
Explain, why is water sprayed on roads in evening in hot summer?
Specific heat capacity of substance A is 3.8 J g-1 K-1whereas the specific heat capacity of substance B is 0.4 J g-1 K-1. Which of the two is a good conductor of heat? How is one led to this conclusion?
Read the passage and answer the questions based on it.
If heat is exchanged between a hot and cold object, the temperature of the cold object goes on increasing due to gain of energy and the temperature of the hot object goes on decreasing due to loss of energy. The change in temperature continues till the temperatures of both objects attain the same value. In this process, the cold object gains heat energy and the hot object loses heat energy. If the system of both the objects is isolated from the environment by keeping it inside a heat-resistant box then no energy can flow from inside the box or come into the box. In this situation, we get the following principle.
Heat energy lost by the hot object = Heat energy gained by the cold object. This is called the ‘Principle of heat exchange’.
- Where does heat transfer take place?
- In such a situation which principle of heat do you perceive?
- How can this principle be explained in short?
- Which property of the substance is measured using this principle?
Numerical Problem.
What is the heat in joules required to raise the temperature of 25 grams of water from 0°C to 100°C? What is the heat in Calories? (Specific heat of water = `(4.18"J")/("g"°"C")`
The value of 'γ' for a gas is given as `gamma = 1 + 2/"f"`, where 'f ' is the number of degrees of freedom of freedom of a molecule of a gas. What is the ratio of `gamma_"monoatonic"//gamma_"diatomic"`?
Diatomic gas consists of rigid gas molecules
Why is water used as a coolant in radiators of a car?
A 0.2 kg metal at 150°C is placed in a copper calorimeter (water equivalent 0.025 kg) with 150 cm³ water at 27°C. Final temperature is 40°C. Find the specific heat of the metal.
