Steam at 100°C is passed into 20 g of water at 10°C. When water acquires a temperature of 80°C, the mass of water present will be (Take specific heat of water=1 cal g-1 °C-1 and latent heat of steam = 540 cal g-1)

(a) 24 g                       

(b) 31.5g

(c) 42.5 g                   

(d) 22.5 g

Subtopic:  Calorimetry |
 68%
From NCERT
NEET - 2014
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A certain quantity of water cools from \(70^{\circ}\mathrm{C}\) to \(60^{\circ}\mathrm{C}\) in the first 5 minutes and to \(54^{\circ}\mathrm{C}\) in the next 5 minutes. 
The temperature of the surroundings will be: 

1. \(45^{\circ}\mathrm{C}\) 2. \(20^{\circ}\mathrm{C}\)
3. \(42^{\circ}\mathrm{C}\) 4. \(10^{\circ}\mathrm{C}\)
Subtopic:  Newton's Law of Cooling |
 77%
From NCERT
NEET - 2014
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A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

(1) Stefan's law

(2) Wien's displacement law

(3) Kirchoff's law

(4) Newton's law of cooling

Subtopic:  Wien's Displacement Law |
 78%
From NCERT
NEET - 2013
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Liquid oxygen at 50K is heated to 300K at constant pressure of 1 atm. The rate of heating is constant.Which one of the following graphs represents the variation of temperature with time?

Subtopic:  Calorimetry |
 74%
From NCERT
NEET - 2012
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A slab of stone of area of 0.36 m2 and 

thickness 0.1 m is exposed on the lower 

surface to steam at 100°C. A block of ice 

at 0°C rests on the upper surface of the slab.

In one hour 4.8 kg of ice is melted. The thermal

conductivity of slab is

(Given latent heat of fusion of ice 

=3.36x105 J kg-1)

(a) 1.24 J/m/s/°C        (b) 1.29 J/m/s/°C

(c) 2.05 J/m/s/°C        (d) 1.02 J/m/s/°C

Subtopic:  Conduction |
 62%
From NCERT
NEET - 2012
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When 1 kg of ice at 0°C melts to water at 0°C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/g, is

(1)  8×104 cal/K                                     

(2)  80 cal/K

(3)  293 cal/K                                         

(4)  273 cal/K

Subtopic:  Calorimetry |
NEET - 2011
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A thermocouple of negligible resistance produces an emf of 40 μV/°C in the linear range of temperature. A galvanometer of resistance 10 Ω whose sensitivity is 1 μA/div, is employed with the thermocouple. The smallest value of temperature difference that can be detected by the system will be

(a) 0.5°C                                       (b) 1°C

(c) 0.1°C                                       (d) 0.25°C

NEET - 2011
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A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reserviors in time t ?

(1)Q/4                                         

(2)Q/16

(3)2Q                                           

(4)Q/2

Subtopic:  Conduction |
 56%
From NCERT
NEET - 2010
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The total radiant energy per unit area per unit time, normal to the direction of incidence, received at a distance R from the centre of a star of radius r,whose outer surface radiates as a black body at a temperature TK is given by 

(a) σr2T4/R2                                       (b) σr2T4/4πr2

(c) σr4T4/r4                                        (d) 4π σr2T4/R2

(where σ is Stefan's constant)

Subtopic:  Stefan-Boltzmann Law |
 61%
From NCERT
NEET - 2010
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A black body at 227°C radiates heat at the rate of 7 cal cm-2s-1. At a temperature of 727°C, the rate of heat radiated in the same units will be 

(1) 60                                     

(2) 50

(3) 112                                   

(4) 80

Subtopic:  Stefan-Boltzmann Law |
 84%
From NCERT
NEET - 2009
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