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
The light from the Sun is found to have a maximum intensity near the wavelength of 470 nm. Assuming the surface of the Sun as a black body, the temperature of the Sun is _____________.
[Wien's constant b = 2 .898 x l0- 3mK]
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
The substance which allows heat radiations to pass through is _______.
(A) iron
(B) water vapour
(C) wood
(D) dry air
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)`
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?
Which of the following pairs may give equal numerical values of the temperature of a body?
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
The temperature of water at the surface of a deep lake is 2°C. The temperature expected at the bottom is
An aluminium sphere is dipped into water at 10°C. If the temperature is increased, the force of buoyancy
Is heat a conserved quantity?
A body A is placed on a railway platform and an identical body B in a moving train. Which of the following energies of B are greater than those of A, as seen from the ground?
(a) Kinetic
(b) Total
(c) Mechanical
(d) Internal
As the temperature is increased, the time period of a pendulum
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?
Water equivalent of a body is measured in ___________ .
When a hot liquid is mixed with a cold liquid, the temperature of the mixture ____________ .
Which of the following pairs of physical quantities may be represented in the same unit?
A concrete slab has a length of 10 m on a winter night when the temperature is 0°C. Find the length of the slab on a summer day when the temperature is 35°C. The coefficient of linear expansion of concrete is 1.0 × 10–5 °C–1.
A metre scale made of steel is calibrated at 20°C to give correct reading. Find the distance between the 50 cm mark and the 51 cm mark if the scale is used at 10°C. Coefficient of linear expansion of steel is 1.1 × 10–5 °C–1.
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 ball that is initially at a pressure of 1.0 × 105 Pa is heated from 20°C to 120°C, keeping its volume constant.
Find the pressure inside the ball. Coefficient of linear expansion of steel = 12 × 10–6 °C–1and bulk modulus of steel = 1.6 × 1011 Nm–2.
Explain the meaning of heat and work with suitable examples.
Temperature in the form of energy.
Give reasons for the following:
Hot metal ball of 80° C is dipped into water of 80°C. The ball will not contract.
Heat given to a body that raises its temperature by 1°C is ______.
The average kinetic energy of molecules of a gas is directly related to which physical quantity?
When two bodies at different temperatures are placed in contact, heat flows from ______.
1 calorie is equal to how many joules?
