# The quantities of heat required to raise the temperature of two solid copper spheres of radii $$r_1$$ and $$r_2$$ $$(r_1=1.5~r_2)$$ through $$1~\text{K}$$ are in the ratio: 1. $$\frac{9}{4}$$ 2. $$\frac{3}{2}$$ 3. $$\frac{5}{3}$$ 4. $$\frac{27}{8}$$

Subtopic:  Conduction |
51%
From NCERT
NEET - 2020
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Three stars $$A,$$ $$B,$$ and $$C$$ have surface temperatures $$T_A,~T_B$$ and $$T_C$$ respectively. Star $$A$$ appears bluish, star $$B$$ appears reddish and star $$C$$ yellowish. Hence:
1. $$T_A>T_B>T_C$$
2. $$T_B>T_C>T_A$$
3. $$T_C>T_B>T_A$$
4. $$T_A>T_C>T_B$$

Subtopic:  Wien's Displacement Law |
68%
From NCERT
NEET - 2020
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A deep rectangular pond of surface area A, containing water (density = $$\rho,$$ specific heat capacity = $$s$$), is located in a region where the outside air temperature is at a steady value of $$-26^{\circ}\mathrm{C}$$. The thickness of the ice layer in this pond at a certain instant is $$x$$. Taking the thermal conductivity of ice as $$k$$, and its specific latent heat of fusion as $$L$$, the rate of increase of the thickness of the ice layer, at this instant, would be given by:
1. $$\frac{26k}{x\rho L-4s}$$
2. $$\frac{26k}{x^2\rho L}$$
3. $$\frac{26k}{x\rho L}$$
4. $$\frac{26k}{x\rho L+4s}$$

Subtopic:  Conduction |
52%
From NCERT
NEET - 2019
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An object kept in a large room having an air temperature of $$25^\circ \text{C}$$ takes $$12$$ minutes to cool from $$80^\circ \text{C}$$ to $$70^\circ \text{C}.$$ The time taken to cool for the same object from $$70^\circ \text{C}$$ to $$60^\circ \text{C}$$ would be nearly:
1. $$10$$ min
2. $$12$$ min
3. $$20$$ min
4. $$15$$ min

Subtopic:  Newton's Law of Cooling |
77%
From NCERT
NEET - 2019
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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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Gravitational force is required for:
1. stirring of liquid
2. convection
3. conduction

Subtopic:  Convection |
76%
From NCERT
AIPMT - 2000
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Which of the following circular rods, (given radius $$r$$ and length $$l$$) each made of the same material and whose ends are maintained at the same temperature will conduct the most heat:

 1 $$r=2r_0;~l=2l_0$$ 2 $$r=2r_0;~l=l_0$$ 3 $$r=r_0;~l=2l_0$$ 4 $$r=r_0;~l=l_0$$
Subtopic:  Conduction |
85%
From NCERT
AIPMT - 2005
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Radiation energy corresponding to the temperature T of the sun is E. If its temperature is doubled, then its radiation energy will be:
1. 32 E
2. 16 E
3. 8 E
4. 4 E

Subtopic:  Stefan-Boltzmann Law |
89%
From NCERT
AIPMT - 1998
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A sphere maintained at a temperature of 600 K, has a cooling rate R in an external environment of 200 K temperature. If its temperature falls to 400 K, then its cooling rate will be:

1. $\frac{3}{16}R$

2. $\frac{16}{3}R$

3. $\frac{9}{27}R$

4. None

Subtopic:  Stefan-Boltzmann Law |
From NCERT
AIPMT - 1999
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If λm denotes the wavelength at which the radioactive emission from a black body at a temperature T K is maximum, then:

1. λm is independent of T

2. λm ∝ T

3. λm ∝ T–1

4. λm ∝ T– 4

Subtopic:  Wien's Displacement Law |
85%
From NCERT
AIPMT - 2004
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