THERMAL PROPERTIES OF MATTER QUIZ-22
Dear Readers,Statement 2: It is given by l=l_0 eα∆T, which cannot be treated as being approximately equal to l=l_0 (1+α∆T) for large value a ∆T
211
Statement 2: The thermal radiations require no medium for propagation
212(b) Light radiations and thermal radiations both belong to electromagnetic spectrum. Light radiations belong to visible region while thermal radiation belong to infrared region to EM spectrum. Also EM radiations requires no medium for propagation
Statement 2: Thermal resistance is the ratio of temperature difference between the ends of the conductor and rate of flow of heat
213(b) (b) R=((θ_1-θ_2))/(ω/t)=l/KA⇒R∝1/K
Q214. Statement 1: As the temperature of the black body increases, the wavelength at which the spectral intensity (E_λ ) is maximum decreases
Statement 2: The wavelength at which the spectral intensity will be maximum for a black body is proportional to the fourth power of its absolute temperature
214 (c) From Wein’s law λ_m T= constant i.e., peak emission wavelength λ_m∝1/T. Hence as T increases λ_m decreases
Statement 2: Heat conduction in a body is directly proportional to cross-sectional area
215 (a) Both are true and Statement II explains Statement I because for same volume, surface area of the cylindrical bulb will be more
Statement 2: For two cylindrical rods of identical size and different thermal conductivity K_1 and K_2 connected in series, the equivalent thermal conductivity K is given by 2/K=1/K_1 +1/K_2
216 (d) Equivalent thermal conductively of two identical rods in series is given by 2/K=1/K_1 +1/K_2 If K_1
Statement 2: According to Kirchoff’s law the absorptivity of a body is equal to its emissivity at a given wavelength
217 (a) According to Kirchoff’s law e_λ/a_λ =E_λ For a particular wavelength E_λ=1⇒e_λ=a_λ ∴ Emissivity = Absorptivity
Statement 2: The temperature at the surface of the moon is much higher than boiling point of the water
218(c) Water evaporates quickly because of lack of atmospheric pressure, also temperature of moon is much higher during day time but it is very low at night
Statement 2: Thermal capacity is the required for raising temperature of unit mass of the body through unit degree
219 (d) Specific heat of a body is the amount of heat required to raise the temperature of unit mass of the body through unit degree. When mass of a body is less than unity, then its thermal capacity is less than its specific heat and vice-versa
Statement 2: The coefficient of volume expansion is defined as the change in volume per unit volume per unit change in temperature
220 (a) As r=∆V/V∆t, i.e., unit of coefficient of volume expansion is K(-1)
