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
A pinhole is made in a hollow sphere of radius 5 cm whose inner wall is at temperature 727oC. Find the power radiated per unit area. [Stefan’s constant σ = 5.7 x 10-8 J/m2 s K4 , emissivity (e) = 0.2]
1000 tiny mercury droplets coalesce to form a bigger drop. In this process, temperature of the drop _______ .
(A) increases
(B) may increase or decrease
(C) decreases
(D) does not change
A body cools from 62°C to 54°C in 10 minutes and to 48°C in the next 10 minutes. Find the temperature of the surroundings.
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?
Can the bulb of a thermometer be made of an adiabatic wall?
Why do marine animals live deep inside a lake when the surface of the lake freezes?
A spherical shell is heated. The volume changes according to the equation Vθ = V0 (1 + γθ). Does the volume refer to the volume enclosed by the shell or the volume of the material making up the shell?
If the temperature of a uniform rod is slightly increased by ∆t, its moment of inertia I about a line parallel to itself will increase by
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
Is heat a conserved quantity?
As the temperature is increased, the time period of a pendulum
A person's skin is more severely burnt when put in contact with 1 g of steam at 100°C than when put in contact with 1 g of water at 100°C. Explain
When a hot liquid is mixed with a cold liquid, the temperature of the mixture ____________ .
Two bodies at different temperatures are mixed in a calorimeter. Which of the following quantities remains conserved?
The mechanical equivalent of heat ____________ .
The volume of a glass vessel is 1000 cc at 20°C. What volume of mercury should be poured into it at this temperature so that the volume of the remaining space does not change with temperature? Coefficients of cubical expansion of mercury and glass are 1.8 × 10–6 °C–1 and 9.0 × 10–6 °C–1 , respectively.
In hot summer after a bath, the body’s __________.
Explain the meaning of heat and work with suitable examples.
Two tumblers of A and B have water at 50°C temperature. If the water from A and B is poured into tumbler C. The temperature of C is ______.
Heat is measured in Celsius or centigrade.
Temperature in the form of energy.
The normal temperature of our body is 37°C.
What is the SI unit of heat?
1 calorie is equal to how many joules?
Which state of matter has particles that vibrate about fixed equilibrium positions?
What is the approximate interatomic spacing in gases at NTP (Normal Temperature and Pressure)?
The concept of thermal equilibrium, where heat flows between bodies until they reach the same temperature, is the basis of which law of thermodynamics?
