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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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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Assuming the sun to have a spherical outer surface of radius r, radiating like a black body at temperature t °C, the power received by a unit surface of the earth (normal to the incident rays) at a distance from the centre of the sun is: 
(where σ is Stefan’s constant.)

1. 4πr2σt4R2

2. r2σ(t+273)44πR2

3. 16π2r2σt4R2

4. r2σ(t+273)4R2

Subtopic:  Radiation |
 65%
From NCERT
AIPMT - 2007
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A black body is at 727 °C. It emits energy at a rate that is proportional to:

1. (727)2

2. (1000)4

3. (1000)2

4. (727)4

Subtopic:  Radiation |
 80%
From NCERT
AIPMT - 2007
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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 copper rod of \(88\) cm and an aluminium rod of an unknown length have an equal increase in their lengths independent of an increase in temperature. The length of the aluminium rod is:
\(\left(\alpha_{Cu}= 1.7\times10^{-5}~\text{K}^{-1}~\text{and}~\alpha_{Al}= 2.2\times10^{-5}~\text{K}^{-1}\right)\)
1. \(68~\text{cm}\)
2. \(6.8~\text{cm}\)
3. \(113.9~\text{cm}\)
4. \(88~\text{cm}\)

Subtopic:  Thermal Expansion |
 76%
From NCERT
NEET - 2019
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In which of the following phenomenon heat convection does not take place

1. land and sea breeze

2. boiling of water

3. heating of glass surface due to filament of the bulb

4. air around the furnace

Subtopic:  Convection |
 75%
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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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The temperature of a body on the Kelvin scale is found to be x K. When it is measured by a Fahrenheit thermometer, it is found to be x°F, then the value of x is:
1. 40

2. 313

3. 574.25

4. 301.25

Subtopic:  Temperature and Heat |
 71%
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In a new temperature scale, freezing point of water is given a value 10x and boiling point of water is 90x. Reading of new temperature scale for a temperature equal to 10°C is 

1.  14x

2.  16x

3.  18x

4.  12x

Subtopic:  Temperature and Heat |
 84%
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