# Two absolute scales $$A$$ and $$B,$$ have triple points of water defined to be $$200 A$$ and $$350 B$$. The relationship between $$T_A$$ and $$T_B$$: 1. $$T_A = {5 \over 7}T_B$$ 2. $$T_A = { 4 \over 7}T_B$$ 3. $$T_A = { 6 \over 7}T_B$$ 4. $$T_A = T_B$$

Subtopic:  Temperature and Heat |
73%
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A brass wire $$1.8$$ m long at $$27$$ °C is held taut with a little tension between two rigid supports. If the wire is cooled to a temperature of$$-39$$ °C, what is the tension created in a wire with a diameter of $$2.0$$ mm? (coefficient of linear expansion of brass $$=2.0 \times10^{-5}$$ K-1, Young's modulus of brass$$=0.91 \times10^{11}$$ Pa)
1. $$3.8 \times 10^3$$ N
2. $$3.8 \times 10^2$$ N
3. $$2.9 \times 10^{-2}$$ N
4. $$2.9 \times 10^{2}$$ N

Subtopic:  Thermal Stress |
67%
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In an experiment on the specific heat of a metal, a 0.20 kg block of the metal at $$150^{\circ}\mathrm{C}$$ is dropped in a copper calorimeter (of water equivalent of 0.025 kg) containing 150 $$c m^{3}$$ of water at $$27^{\circ}\mathrm{C}$$. The final temperature is $$40^{\circ}\mathrm{C}$$. The specific heat of the metal will be: (Heat   losses   to   the   surroundings   are   negligible)
1. $$0 . 40 ~ \text{Jg}^{- 1} \text{K}^{- 1}$$

2. $$0 . 43 ~ \text{Jg}^{- 1} \text{K}^{- 1}$$
3. $$0 . 54 ~ \text{Jg}^{- 1} \text{K}^{- 1}$$
4. $$0 . 61 ~ \text{Jg}^{- 1} \text{K}^{- 1}$$

Subtopic:  Calorimetry |
60%
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The diagram shows a bimetallic strip used as a thermostat in a circuit. Copper expands more than Invar for the same temperature rise.

What will be switched on when the bimetallic strip becomes hot?

 1 bell only 2 lamp and bell only 3 motor and bell only 4 lamp, bell, and motor

Subtopic:  Thermal Expansion |
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A piece of iron is heated in a flame. If it becomes dull red first, 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 Kirchhoff's law 4 Newton's law of cooling
Subtopic:  Wien's Displacement Law |
81%
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5 g of water at $$30^{\circ} \mathrm{C}$$ and 5 g of ice at $$-20^{\circ} \mathrm{C}$$ are mixed together in a calorimeter. The water equivalent of the calorimeter is negligible, and the specific heat and latent heat of ice are 0.5 $$\text{cal/g}^{\circ} \mathrm{C}$$ and 80 $$\text{cal/g}$$, respectively. The final temperature of the mixture is:

 1 $$0^{\circ} \mathrm{C}$$ 2 $$-8^{\circ} \mathrm{C}$$ 3 $$-4^{\circ} \mathrm{C}$$ 4 $$2^{\circ} \mathrm{C}$$
Subtopic:  Calorimetry |
72%
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Three rods made of the same material, having the same cross-sectional area but different lengths 10 cm, 20 cm and 30 cm are joined as shown. The temperature of the junction will be:-

1. $$10.8^{\circ}\mathrm{C}$$
2. $$14.6^{\circ}\mathrm{C}$$
3. $$16.4^{\circ}\mathrm{C}$$
4. $$18.2^{\circ}\mathrm{C}$$

Subtopic:  Conduction |
70%
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Four rods of the same material with different radii and length $\mathcal{l}$ are used to connect two heat reservoirs at different temperatures. In which of the following cases is the heat conduction fastest?

1. $r=\frac{1}{3}\mathrm{cm},$ $\mathcal{l}=\frac{1}{9}\mathrm{cm}$

2. r = 3 cm, $\mathcal{l}$ = 9 cm

3. r = 4 cm, $\mathcal{l}$ = 8 cm

4. r = 1 cm, $\mathcal{l}$ = 1 cm

Subtopic:  Conduction |
73%
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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 |
63%
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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: $\mathrm{\pi }$

2. 1: 2

3. $\mathrm{\pi }$: 2

4. 3: 2

Subtopic:  Conduction |
66%
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