Advertisements
Advertisements
प्रश्न
Define emissive power and coefficient of emmision of a body.
Advertisements
उत्तर
Emissive power of a body at a given temperature is the quantity of radiant energy emitted by the body per unit time per unit surface area of the body at that temperature.
If ‘Q’ is the amount of radiant energy emitted, ‘A’ is the surface area of the body and ‘t’ is the time for which body radiates energy, then the emissive power is
`E=Q/(at)`
Coefficient of emission of a body is the ratio of the emissive power of the body at agiven temperature to the emissive power of a perfectly black body at the same temperature.
Coefficient of emission, `e=E/E_b`
APPEARS IN
संबंधित प्रश्न
Two copper spheres of radii 6 cm and 12 cm respectively are suspended in an evacuated enclosure. Each of them are at a temperature 15°C above the surroundings. The ratio of their rate of loss of heat is.................
- 2:1
- 1:4
- 1:8
- 8:1
Compute the temperature at which the r.m.s. speed of nitrogen molecules is 832 m/s. [Universal gas constant, R = 8320 J/k mole K, molecular weight of nitrogen = 28.]
The susceptibility of magnesium at 300 K is 2.4 x 10-5. At what temperature will the susceptibility increase to 3.6 x 10-5?
What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?
The kinetic energy per molecule of a gs at temperature T is ________.
(a) `(3/2)RT`
(b) `(3/2)K_BT`
(c) `(2/3) RT`
(d) `(3/2)("RT"/M)`
It is said that mercury is used in defining the temperature scale because it expands uniformly with temperature. If the temperature scale is not yet defined, is it logical to say that a substance expands uniformly with temperature?
The density of water at 4°C is supposed to be 1000 kg m–3. Is it same at sea level and at high altitude?
Which of the curves in the following figure represents the relation between Celsius and Fahrenheit temperatures?
An aluminium sphere is dipped into water at 10°C. If the temperature is increased, the force of buoyancy
A spinning wheel is brought in contact with an identical wheel spinning at identical speed. The wheels slow down under the action of friction. Which of the following energies of the first wheel decreases?
(a) Kinetic
(b) Total
(c) Mechanical
(d) Internal
When a solid melts or a liquid boils, the temperature does not increase even when heat is supplied. Where does the energy go?
Should a thermometer bulb have large heat capacity or small heat capacity?
Two bodies at different temperatures are mixed in a calorimeter. Which of the following quantities remains conserved?
A resistance thermometer reads R = 20.0 Ω, 27.5 Ω, and 50.0 Ω at the ice point (0°C), the steam point (100°C) and the zinc point (420°C), respectively. Assuming that the resistance varies with temperature as Rθ = R0 (1 + αθ + βθ2), find the values of R0, α and β. Here θ represents the temperature on the Celsius scale.
The densities of wood and benzene at 0°C are 880 kg m3 and 900 kg m–3 , respectively. The coefficients of volume expansion are 1.2 × 10–3 °C–1 for wood and 1.5 × 10–3 °C–1for benzene. At what temperature will a piece of wood just sink in benzene?
A steel rod of length 1 m rests on a smooth horizontal base. If it is heated from 0°C to 100°C, what is the longitudinal strain developed?
A steel wire of cross-sectional area 0.5 mm2 is held between two fixed supports. If the wire is just taut at 20°C, determine the tension when the temperature falls to 0°C. Coefficient of linear expansion of steel is 1.2 × 10–5 °C–1 and its Young's modulus is 2.0 × 10–11 Nm–2.
In hot summer after a bath, the body’s __________.
Define one mole.
Temperature and Heat are ______
Two objects are said to be in thermal contact if they can exchange heat energy.
One day in 1922, the air temperature was measured at 59°C in the shade in Libya ______.
Analogy
Evaporation:: 100°C: Freezing:: ______.
Heat given to a body that raises its temperature by 1°C is ______.
The temperature of a liquid drops from 365 K to 361 K in 2 min. Find the time during which the temperature of the liquid drops from 344 K to 342 K.
(Take, room temperature = 293 K)
Which conversion is numerically correct for heat energy?
In the formula Q = mcΔT, what does c represent?
What condition defines thermal equilibrium between two bodies?
