# 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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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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On observing light from three different stars $$P$$, $$Q$$, and $$R$$, it was found that the intensity of the violet colour is maximum in the spectrum of $$P$$, the intensity of the green colour is maximum in the spectrum of $$R$$ and the intensity of the red colour is maximum in the spectrum of $$Q$$. If $$T_P$$$$T_Q$$, and $$T_R$$ are the respective absolute temperatures of $$P$$, $$Q$$, and $$R$$, then it can be concluded from the above observations that:
1. $$T_P>T_Q>T_R$$
2. $$T_P>T_R>T_Q$$
3. $$T_P<T_R<T_Q$$
4. $$T_P<T_Q<T_R$$

Subtopic:  Wien's Displacement Law |
65%
From NCERT
NEET - 2015
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The coefficient of linear expansion of brass and steel rods are $$\alpha_1$$ and $$\alpha_2$$. Lengths of brass and steel rods are $$L_1$$ and $$L_2$$ respectively. If $$(L_2-L_1)$$ remains the same at all temperatures, which one of the following relations holds good?
1. $$\alpha_1L_2^2=\alpha_2L_1^2$$
2. $$\alpha_1^2L_2=\alpha_2^2L_1$$
3. $$\alpha_1L_1=\alpha_2L_2$$
4. $$\alpha_1L_2=\alpha_2L_1$$

Subtopic:  Thermal Expansion |
88%
From NCERT
NEET - 2016
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Two rods $$A$$ and $$B$$ of different materials are welded together as shown in the figure. Their thermal conductivities are $$K_1$$ and $$K_2.$$ The thermal conductivity of the composite rod will be:

 1 $$\frac{3(K_1+K_2)}{2}$$ 2 $$K_1+K_2$$ 3 $$2(K_1+K_2)$$ 4 $$\frac{(K_1+K_2)}{2}$$
Subtopic:  Conduction |
72%
From NCERT
NEET - 2017
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A black body at $$200$$ K is found to emit maximum energy at a wavelength of $$14$$ $$\mu$$m. When its temperature is raised to $$1000$$ K, the wavelength at which maximum energy is emitted will be:

 1 $$14$$ $$\mu$$m 2 $$70$$ $$\mu$$m 3 $$2.8$$ $$\mu$$m 4 $$2.8$$ nm
Subtopic:  Wien's Displacement Law |
86%
From NCERT
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The triple points of neon and carbon dioxide are $$24.57$$ K and $$216.55$$ K respectively. The value of these temperatures on Fahrenheit scales will be:

 1 $$-415.44^\circ ~\mathrm{F} ,~-69.88^\circ ~\mathrm{F}$$ 2 $$-248.58^\circ ~\mathrm{F} ,~-56.60^\circ~ \mathrm{F}$$ 3 $$315.44^\circ ~\mathrm{F} ,~-69.88^\circ ~\mathrm{F}$$ 4 $$415.44^\circ ~\mathrm{F} ,~-79.88^\circ~ \mathrm{F}$$

Subtopic:  Temperature and Heat |
66%
From NCERT
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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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The coefficient of area expansion $$\beta$$ of a rectangular sheet of a solid in terms of the coefficient of linear expansion $$\alpha$$ is:
1. $$2\alpha$$
2. $$\alpha$$
3. $$3\alpha$$
4. $$\alpha^2$$

Subtopic:  Thermal Expansion |
90%
From NCERT
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When $$0.15$$ kg of ice at $$0^\circ \text{C}$$ is mixed with $$0.30$$ kg of water at $$50^\circ \text{C}$$ in a container, the resulting temperature is $$6.7^\circ \text{C}.$$
The heat of fusion of ice is: ($$S_{\text{water}}=4186$$ J kg-1 K-1)
1. $$3.43 \times 10^4$$ Jkg-1
2. $$3.34 \times 10^4$$ Jkg-1
3. $$3.34 \times 10^5$$ Jkg-1
4. $$4.34 \times 10^5$$ Jkg-1

Subtopic:  Calorimetry |
57%
From NCERT
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