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Q 27 ofMark for reviewThe SI Unit of thermal stressisJoule |
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Answer» Explanation: Temperature and Heat In this section of the chapter, you will learn about the heat and temperature and also about their S.I Unit and the relationship of Fahrenheit and CELSIUS. Heat is the form of energy transferred between two or more systems and its surroundings by virtue of the temperature difference. The S.I unit of heat energy is transferred in Joule (J); 1 cal = 4.186 J Temperature, as defined in the chapter, is the degree of coldness or hotness of the substance. The S.I. unit of temperature is Kelvin (K) and ℃ is the most common unit of temperature. The temperature of a body is measured with the help of a thermometer. The two different scales of temperature Fahrenheit and Celsius are mentioned and the relationship between them is explained. where tc and tf are temperature values of the body on Celsius and Fahrenheit scale. Thermal Expansion Thermal expansion is an increase in the size of a body DUE to temperature. Three different types of expansions have been explained in this chapter which is as mentioned below: Linear Expansion: The increase in the length of a solid on heating is called linear expansion. It is given by the EQUATION: l = l ∞t where l is the original length of any solid, ∆t is the increase in the temperature of the rod. The length so increased is shown by ∆l Superficial Expansion: The increase in the surface area of the solid is known as superficial expansion. Volume Expansion: The increase in the volume of the solid is known as volume expansion. The relationship between the three types of equation is shown by the below equation: Where α, β and γ are not constant, they depend on the temperature range. Newton’s Law of Cooling It is one of the important laws covered under the chapter which states that the rate of heat LOSS of a body is directly proportional to the differences in temperatures between the body and its surroundings. Some more important topics are discussed in this chapter. Important formulae covered in this chapter Thermal Stress = Thermal stress = Y α ∆ t Basic Heat formula Q = m * S * t i.e, Heat required = MASS * specific heat * change in temperature Heat Transfer where K is called thermal conductivity and A is an area of cross-section. |
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