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प्रश्न
The substance which allows heat radiations to pass through is _______.
(A) iron
(B) water vapour
(C) wood
(D) dry air
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उत्तर
dry air
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संबंधित प्रश्न
A metal sphere cools at the rate of 4°C / min. when its temperature is 50°C. Find its rate of cooling at 45°C if the temperature of surroundings is 25°C.
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
The dimensions of emissive power are ______.
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]
A metal ball cools from 64 °C to 50 °C in 10 minutes and to 42 °C in next 10 minutes. The ratio of rates of fall of temperature during the two intervals is _______.
A body cools from 80° C to 70° C in 5 minutes and to 62° C in the next 5 minutes. Calculate the temperature of the surroundings.
The length of a brass rod is found to be less on a hot summer day than on a cold winter day as measured by the same aluminium scale. Can we conclude that brass shrinks on heating?
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?
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?
When a solid melts or a liquid boils, the temperature does not increase even when heat is supplied. Where does the energy go?
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
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?
The heat capacity of a body depends on
(a) the heat given
(b) the temperature raised
(c) the mass of the body
(d) the material of the body
If heat is supplied to a solid, its temperature
(a) must increase
(b) may increase
(c) may remain constant
(d) may decrease
Heat and work are equivalent. This means, ____________ .
A railway track (made of iron) is laid in winter when the average temperature is 18°C. The track consists of sections of 12.0 m placed one after the other. How much gap should be left between two such sections, so that there is no compression during summer when the maximum temperature rises to 48°C? Coefficient of linear expansion of iron = 11 × 10–6 °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.
Define one mole.
Our normal body temperature is ______.
Two objects are said to be in thermal contact if they can exchange heat energy.
Heat is measured in Celsius or centigrade.
Two identical beakers A and B contain equal volumes of two different liquids at 60°C each and is left to cool down. Liquid in A has a density of 8 × 102 kg/m3 and specific heat of 2000 J kg-1 K-1 while the liquid in B has a density of 103 kg m-3 and specific heat of 4000 J kg-1 K-1. Which of the following best describes their temperature versus time graph schematically? (assume the emissivity of both the beakers to be the same.)
Heat given to a body that raises its temperature by 1°C is ______.
The concept of thermal equilibrium, where heat flows between bodies until they reach the same temperature, is the basis of which law of thermodynamics?
