# Three rods made of the same material and having the same cross-section have been joined as shown in the figure. Each rod has the same length. The left and right ends are kept at $$0^{\circ}\text{C}~\text{and}~90^{\circ}\text{C},$$ respectively. The temperature at the junction of the three rods will be:             1. $$45^{\circ}\text{C}$$ 2. $$60^{\circ}\text{C}$$ 3. $$30^{\circ}\text{C}$$ 4. $$20^{\circ}\text{C}$$

Subtopic:  Conduction |
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Hot coffee in a mug cools from $$90^{\circ}\mathrm{C}$$ to $$70^{\circ}\mathrm{C}$$ in 4.8 minutes. The room temperature is $$20^{\circ}\mathrm{C}$$. Applying Newton's law of cooling, the time needed to cool it further by $$10^{\circ}\mathrm{C}$$ should be nearly:

 1 4.2 minute 2 3.8 minute 3 3.2 minute 4 2.4 minute
Subtopic:  Newton's Law of Cooling |
70%
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One kilogram of ice at $$0^\circ \mathrm{C}$$ is mixed with one kilogram of water at $$80^\circ \mathrm{C}.$$ The final temperature of the mixture will be: (Take: Specific heat of water = $$4200$$ J kg-1 K-1, latent heat of ice$$=336$$ kJ kg-1)

 1 $$0^\circ \mathrm{C}$$ 2 $$50^\circ \mathrm{C}$$ 3 $$40^\circ \mathrm{C}$$ 4 $$60^\circ \mathrm{C}$$
Subtopic:  Calorimetry |
74%
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The value of the coefficient of volume expansion of glycerin is $$5\times10^{-4}$$ K-1. The fractional change in the density of glycerin for a temperature increase of $$40^\circ \mathrm{C}$$ will be:

 1 $$0.015$$ 2 $$0.020$$ 3 $$0.025$$ 4 $$0.010$$
Subtopic:  Thermal Expansion |
82%
From NCERT
NEET - 2015
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Steam at $$100^{\circ}\mathrm{C}$$ is injected into 20 g of $$10^{\circ}\mathrm{C}$$ water. When water acquires a temperature of $$80^{\circ}\mathrm{C}$$, the mass of water present will be: (Take specific heat of water =1 cal g-1 $$^\circ$$C-1 and latent heat of steam = 540 cal g-1)

 1 24 g 2 31.5g 3 42.5 g 4 22.5 g
Subtopic:  Calorimetry |
71%
From NCERT
NEET - 2014
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The temperature of a body falls from $$50^{\circ}\mathrm{C}$$$\mathrm{}$ to $$40^{\circ}\mathrm{C}$$$\mathrm{}$ in 10 minutes. If the temperature of the surroundings is $$20^{\circ}\mathrm{C}$$$\mathrm{, t}$hen the temperature of the body after another 10 minutes will be:
1. $$36.6^{\circ}\mathrm{C}$$
2. $$33.3^{\circ}\mathrm{C}$$$\mathrm{}$
3. $$35^{\circ}\mathrm{C}$$
4. $$30^{\circ}\mathrm{C}$$$\mathrm{}$

Subtopic:  Newton's Law of Cooling |
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Two rods (one semi-circular and the other straight) of the same material and of the same cross-sectional area are joined as shown in the figure. Points $$A$$ and $$B$$ are maintained at different temperatures. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a cross-section of a straight rod at any given point in time will be:

1. $$2:\pi$$
2. $$1:2$$
3. $$\pi:2$$
4. $$3:2$$

Subtopic:  Conduction |
66%
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The plots of intensity versus wavelength for three black bodies at temperatures ${\mathrm{T}}_{1}$${\mathrm{T}}_{2}$ and ${\mathrm{T}}_{3}$ respectively are as shown. Their temperatures are such that:

 1 $$\mathrm{T}_1>\mathrm{T}_2>\mathrm{T}_3$$ 2 $$\mathrm{T}_1>\mathrm{T}_3>\mathrm{T}_2$$ 3 $$\mathrm{T}_2>\mathrm{T}_3>\mathrm{T}_1$$ 4 $$\mathrm{T}_3>\mathrm{T}_2>\mathrm{T}_1$$
Subtopic:  Wien's Displacement Law |
64%
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Two rods, one made of aluminium and the other made of steel, having initial lengths $$l_1$$ and $$l_2$$ are connected together to form a single rod of length ${l}_{1}+{l}_{2}$. The coefficient of linear expansion for aluminium and steel are ${\alpha }_{a}$ and ${\alpha }_{s}$ respectively. If the length of each rod increases by the same amount when their temperature is raised by $$t^\circ \mathrm{C},$$ then the ratio $$\frac{l_1}{l_1+l_2}$$ is:
1. $\frac{{\alpha }_{s}}{{\alpha }_{a}}$

2. $\frac{{\alpha }_{a}}{{\alpha }_{s}}$

3. $\frac{{\alpha }_{a}}{{\alpha }_{a}+{\alpha }_{s}}$

4. $\frac{{\alpha }_{s}}{{\alpha }_{a}+{\alpha }_{s}}$

Subtopic:  Thermal Expansion |
59%
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Four rods of the same material with different radii $$r$$ and length $$l$$ are used to connect two heat reservoirs at different temperatures. In which of the following cases is the heat conduction fastest?
1. $$r = \frac{1}{3}~\text{cm}, l = \frac{1}{9}~\text{cm}$$
2. $$r =3~\text{cm}, l =9~\text{cm}$$
3. $$r =4~\text{cm}, l =8~\text{cm}$$
4. $$r =1~\text{cm}, l =1~\text{cm}$$

Subtopic:  Conduction |
73%
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