MHT CET 2021 23th September Morning Shift | Heat and Thermodynamics Question 100 | Physics

Two rods of different metals have coefficients of linear expansion '$$\alpha_1$$' and '$$\alpha_2$$' respectvely. Their respective lengths are '$$\mathrm{L}_1$$' and '$$\mathrm{L}_2$$'. At all temperatures ($$\mathrm{L}_2-\mathrm{L}_1$$) is same. The correct relation is

$$\mathrm{L}_1 \alpha_1^2=\mathrm{L}_2 \alpha_2^2$$

$$\mathrm{L}_1^2 \alpha_1^2=\mathrm{L}_2^2 \alpha_2^2$$

$$\mathrm{L}_1 \alpha_2=\mathrm{L}_2 \alpha_1$$

$$\mathrm{L}_1 \alpha_1=\mathrm{L}_2 \alpha_2$$

MHT CET 2021 23th September Morning Shift

MCQ (Single Correct Answer)

-0

The temperature of a black body is increased by $$50 \%$$, then the percentage increase in the rate of radiation by the body is approximated

50%

100%

400%

150%

MHT CET 2021 22th September Evening Shift

MCQ (Single Correct Answer)

-0

The emissive power of sphere of area $$0.04 \mathrm{~m}^2$$ is $$0.7 \mathrm{~k} \mathrm{~cal} \mathrm{~s}^{-1} \mathrm{~m}^{-2}$$. The amount of heat radiated in 20 second is

$$2.8 \mathrm{~k} \mathrm{~cal} \mathrm{~s}^{-1} \mathrm{~m}^{-2}$$

$$0.28 \mathrm{~k} \mathrm{~cal} \mathrm{~s}^{-1} \mathrm{~m}^{-2}$$

$$5.6 \mathrm{~k} \mathrm{~cal} \mathrm{~s}^{-1} \mathrm{~m}^{-2}$$

$$0.56 \mathrm{~k} \mathrm{~cal} \mathrm{~s}^{-1} \mathrm{~m}^{-2}$$

MHT CET 2021 22th September Evening Shift

MCQ (Single Correct Answer)

-0

The rate of flow of heat through a copper rod with temperature difference $$28^{\circ} \mathrm{C}$$ is $$1400 \mathrm{~cal} \mathrm{~s}^{-1}$$. The thermal resistance of copper rod will be

$$0.05 \frac{{ }^{\circ} \mathrm{C} \mathrm{s}}{\mathrm{cal}}$$

$$0.02 \frac{{ }^{\circ} \mathrm{C} \mathrm{s}}{\mathrm{cal}}$$

$$5 \frac{{ }^{\circ} \mathrm{C} \mathrm{s}}{\mathrm{cal}}$$

$$2 \frac{{ }^{\circ} \mathrm{Cs}}{\text { cal }}$$

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