Two metal rods \((1)\) and \((2)\) of the same length have the same temperature difference between their ends. Their thermal conductivities are \({K}_1\) and \({K}_2\) and cross-sectional areas \({A}_{1}\) and \({A}_{2},\) respectively. If the rate of heat conduction in \((1)\) is four times that in \((2),\) then:
1. \(K_1 A_1=4K_2 {A}_2 \)
2. \(K_1 {A}_1=2 {K}_2 {A}_2 \)
3. \(4 {K}_1{A}_1={K}_2 {A}_2 \)
4. \({K}_1 {A}_1={K}_2 {A}_2\)

Subtopic:  Conduction |
 74%
From NCERT
NEET - 2013
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The density of water at \(20^\circ \text{C}\) is \(998\) kg/m3 and at \(40^\circ \text{C}\) is \(992\) kg/m3. The coefficient of volume expansion of water is: 
1. \(3 \times 10^{-4} / ^\circ\text C\)
2. \(2 \times 10^{-4} / ^\circ\text C\)
3. \(6 \times 10^{-4} / ^\circ\text C\)
4. \(10^{-4} / ^\circ\text C\)
Subtopic:  Thermal Expansion |
 72%
From NCERT
NEET - 2013
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A slab of stone with an area \(0.36~\text{m}^{2}\) and thickness of \(0.1~\text{m}\) is exposed on the lower surface to steam at \(100​​^{\circ}\mathrm{C}\). A block of ice at \(0^{\circ}\mathrm{C}\) rests on the upper surface of the slab. In one hour \(4.8~\text{kg}\) of ice is melted. The thermal conductivity of the slab will be: (Given latent heat of fusion of ice \(= 3.36\times10^{5}~\text{JKg}^{-1}\))
1. \(1.29~\text{J/m/s/}^{\circ}\text{C}\)
2. \(2.05~\text{J/m/s/}^{\circ}\text{C}\)
3. \(1.02~\text{J/m/s/}^{\circ}\text{C}\)
4. \(1.24~\text{J/m/s/}^{\circ}\text{C}\)

Subtopic:  Conduction |
 58%
From NCERT
AIPMT - 2012
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A black body at 1227 °C emits radiations with maximum intensity at a wavelength of 5000 Å. If the temperature of the body is increased by 1000 °C, the maximum intensity will be observed at:

1. 4000 Å

2. 5000 Å

3. 6000 Å

4. 3000 Å

Subtopic:  Wien's Displacement Law |
 57%
From NCERT
AIPMT - 2006
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A black body is at \(727^\circ\text C.\) It emits energy at a rate that is proportional to:
1. \((727)^2\)
2. \((1000)^4\)
3. \((1000)^2\)
4. \((727)^4\)

Subtopic:  Stefan-Boltzmann Law |
 80%
From NCERT
AIPMT - 2007
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Assuming the sun to have a spherical outer surface of radius \(r,\) radiating like a black body at temperature \(t^\circ\text C,\) the power received by a unit surface of the earth (normal to the incident rays) at a distance \(R\) from the centre of the sun is: (where \(\sigma\) is Stefan's constant.)
1. \(\dfrac{4\pi r^2\sigma t^4}{R^2}\)

2. \(\dfrac{r^2\sigma(t+273)^4}{4\pi R^2}\)

3. \(\dfrac{16\pi^2r^2\sigma t^4}{R^2}\)

4. \(\dfrac{r^2\sigma(t+273)^4}{R^2}\)

Subtopic:  Stefan-Boltzmann Law |
 65%
From NCERT
AIPMT - 2007
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If the cold junction of a thermocouple is kept at 0 °C and the hot junction is kept at T °C, then the relation between neutral temperature (Tn) and temperature of inversion (Ti) is:

1. Tn=Ti2

2. Tn= 2Ti

3. TnTi - T

4. Tn= Ti + T

Subtopic:  Calorimetry |
AIPMT - 2007
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On a new scale of temperature, which is linear and called the \(\mathrm{W}\) scale, the freezing and boiling points of water are \(39^\circ ~\mathrm{W}\)and \(239^\circ ~\mathrm{W}\) respectively. What will be the temperature on the new scale corresponding to a temperature of \(39^\circ ~\mathrm{C}\) on the Celsius scale?
1. \(78^\circ ~\mathrm{C}\)
2. \(117^\circ ~\mathrm{W}\)
3. \(200^\circ ~\mathrm{W}\)
4. \(139^\circ ~\mathrm{W}\)

Subtopic:  Temperature and Heat |
 83%
From NCERT
AIPMT - 2008
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The two ends of a rod of length L and a uniform cross-sectional area A are kept at two temperatures T1 and T2 (T1> T2). The rate of heat transfer dQdt through the rod in a steady state is given by:

1. dQdt=KL(T1-T2)A

2. dQdt=K(T1-T2)LA

3. dQdt=KLA(T1-T2)

4. dQdt=KA(T1-T2)L

Subtopic:  Conduction |
 89%
From NCERT
AIPMT - 2009
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A black body at \(227^{\circ}~\mathrm{C}\) radiates heat at the rate of \(7~ \mathrm{cal-cm^{-2}s^{-1}}\).  At a temperature of \(727^{\circ}~\mathrm{C}\), the rate of heat radiated in the same units will be:
1. \(60\)
2. \(50\)
3. \(112\)
4. \(80\)

Subtopic:  Stefan-Boltzmann Law |
 86%
From NCERT
AIPMT - 2009
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