Heat Transfer PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Heat Transfer · Set 1 (Q1-30)
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1. $An ideal black body at room temperature is thrown into a furnace. It is observed that$ (1) $Initially it is the darkest body and at later times the brightest$ (2) $It is the darkest body at all times$ (3) $It cannot be distinguished at all times$ (4) $Initially it is the darkest body and at later times it cannot be distinguished$ 2. $Consider two hot bodies B_{1} and B_{2} which have temperatures 10 0^{o} C and 8 0^{o} C respectively at t = 0 . The temperature of the surroundings is 4 0^{o} C . The ratio of the respective rates of cooling R_{1} and R_{2} of these two bodies at t = 0 will be$ (1) $R_{1} : R_{2} = 3 : 2$ (2) $R_{1} : R_{2} = 5 : 4$ (3) $R_{1} : R_{2} = 2 : 3$ (4) $R_{1} : R_{2} = 4 : 5$ 3. $A black body of surface area 10 c m^{2} is heated to 127°C and is suspended in a room at temperature 27°C. The initial rate of loss of heat from the body at the room temperature will be$ (1) $2.99 W$ (2) $1.89 W$ (3) $1.18 W$ (4) $0.99 W$ 4. $Relation between the colour and the temperature of a star is given by$ (1) $Wein’s displacement law$ (2) $Planck’s law$ (3) $Hubble’s law$ (4) $Fraunhofer diffraction law$ 5. $A hot liquid cools from 70°C to 60°C in 5 minutes. The time needed by same liquid to cool from 60°C to 50°C will be-$ (1) $Less than 5 minutes$ (2) $More than 5 minutes$ (3) $Equal to 5 minutes$ (4) $Less or more than 5 minutes that depends on the density of liquid$ 6. $A 750 Hz, 20 V (rms) source is connected to a resistance of 100Ω, an inductance of 0.1803 H and a capacitance of 10 μ F all in series. The time in which the resistance (heat capacity 2 J /^{\circ} C will get heated by 10^{\circ} C . (assume no loss of heat to the surroudings) is close to$ (1) $348 s$ (2) $418 s$ (3) $245 s$ (4) $365 s$ 7. $The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is$ (1) $300 : 1$ (2) $600 : 1$ (3) $900 : 1$ (4) $1200 : 1$ 8. $On a clear sunny day, an object at temperature T is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object at the top of the mountain will register a temperature$ (1) $Higher than the object at the foot$ (2) $Lower than the object at the foot$ (3) $Equal to the object at the foot$ (4) $None of the above$ 9. $When red glass is heated in dark room it will seem$ (1) $Green$ (2) $Purple$ (3) $Black$ (4) $Yellow$ 10. $The maximum energy in the thermal radiation from a hot source occurs at a wavelength of 11 \times 1 0^{- 5} cm . According to Wein's law, the temperature of the source (on Kelvin scale) will be n times the temperature of another source (on Kelvin scale) for which the wavelength at maximum energy is 5.5 \times 1 0^{- 5} cm . The value n is$ (1) $2$ (2) $4$ (3) $\frac{1}{2}$ (4) $1$ 11. $Which of the following is the example of ideal black body$ (1) $Kajal$ (2) $Black board$ (3) $A pin hole in a box$ (4) $None of these$ 12. $If the temperature of a black body be increased from 27 to 327 the radiation emitted increases by a fraction of$ (1) $16$ (2) $8$ (3) $4$ (4) $2$ 13. $Which of the following statement is correct$ (1) $A good absorber is a bad emitter$ (2) $Every body absorbs and emits radiations at every temperature$ (3) $The energy of radiations emitted from a black body is same for all wavelengths$ (4) $The law showing the relation of temperatures with the wavelength of maximum emission from an ideal black body is Plank’s law$ 14. $The two ends of a metal rod are maintained at temperatures 100ºC and 110ºC. The rate of heat flow in the rod is found to be 4.0 J/s. If the ends are maintained at temperatures 200ºC and 210ºC, the rate of heat flow will be:$ (1) $16.8 J/s$ (2) $8.0 J/s$ (3) $4.0 J/s$ (4) $44.0 J/s$ 15. $The energy spectrum of a black body exhibits a maximum around a wavelength λ_{0} . The temperature of the black body is now changed such that the energy is maximum around a wavelength \frac{3 λ _{0}}{4} . The power radiated by the black body will now increase by a factor of$ (1) $256/81$ (2) $64/27$ (3) $16/9$ (4) $4/3$ 16. $A black body emits radiations of maximum intensity at a wavelength of 5000 A ˚, when the temperature of the body is 122 7^{o} C . If the temperature of the body is increased by 100 0^{o} C, the maximum intensity of emitted radiation would be observed at$ (1) $2754.8 A ˚$ (2) $3000 A ˚$ (3) $3500 A ˚$ (4) $4000 A ˚$ 17. $Newton's law of cooling is used in laboratory for the determination of the$ (1) $Specific heat of the gases$ (2) $The latent heat of gases$ (3) $Specific heat of liquids$ (4) $Latent heat of liquids$ 18. $A liquid cools down from 7 0^{o} C to 6 0^{o} C in 5 minutes. The time taken to cool it from 6 0^{o} C to 5 0^{o} C will be$ (1) $5 minutes$ (2) $Lesser than 5 minutes$ (3) $Greater than 5 minutes$ (4) $Lesser or greater than 5 minutes depending upon the density of the liquid$ 19. $If the temperature of the body is increased by 10%, the percentage increase in the emitted radiation will be$ (1) $46%$ (2) $40%$ (3) $30%$ (4) $80%$ 20. $A black body is at a temperature of 2880K. The energy of radiation emitted by this object with wave length between 499 nm and 500 nm is U_{1}, between 999 nm and 1000 nm is U_{2} and between 1499 nm and 1500 nm is U_{3} . Wein constant b=2.88 x 1 0^{6} nmK. Then$ (1) $U_{1} = 0$ (2) $U_{3} = 0$ (3) $U_{1} = U_{2}$ (4) $U_{2} > U_{1}$ 21. $According to Newton's law of cooling, the rate of cooling of a body is proportional to (Δ θ)^{n}, where Δθ is the difference of the temperature of the body and the surroundings, and n is equal to$ (1) $2$ (2) $3$ (3) $4$ (4) $1$ 22. $Two spheres of same material have radius 1m and 4 m and temperature 4000K and 2000K respectively. The energy radiated per second by the first sphere is$ (1) $Greater than that by the second$ (2) $Less than that by the second$ (3) $Equal in both cases$ (4) $The information is incomplete$ 23. $Four pieces of iron heated in a furnace to different temperatures show different colours listed below. Which one has the highest temperature$ (1) $White$ (2) $Yellow$ (3) $Orange$ (4) $Red$ 24. $Which of the following statements is true/correct$ (1) $During clear nights, the temperature rises steadily upward near the ground level$ (2) $Newton's law of cooling, an approximate form of Stefan's law, is valid only for natural convection$ (3) $The total energy emitted by a black body per unit time per unit area is proportional to the square of its temperature in the Kelvin scale$ (4) $Two spheres of the same material have radii 1 m and S_{1} and temperatures 4000 K and 2000 K respectively. The energy radiated per second by the first sphere is greater than that radiated per second by the second sphere$ 25. $In rainy season, on a clear night the black seat of a bicycle becomes wet because$ (1) $It absorbs water vapour$ (2) $Black seat is good absorber of heat$ (3) $Black seat is good radiator of heat energy$ (4) $None of the above$ 26. $A metallic sphere cools from 50^{\circ} C to 40^{\circ} C in 300 s. If atmospheric temperature around is 20^{\circ} C, then the sphere's temperature after the next 5 minutes will be close to$ (1) $28^{\circ} C$ (2) $35^{\circ} C$ (3) $33^{\circ} C$ (4) $31^{\circ} C$ 27. $The wavelength of radiation emitted by a body depends upon$ (1) $The nature of its surface$ (2) $The area of its surface$ (3) $The temperature of its surface$ (4) $All the above factors$ 28. $If the initial temperatures of metallic sphere and disc, of the same mass, radius and nature are equal, then the ratio of their rate of cooling in same environment will be$ (1) $1 : 4$ (2) $4 : 1$ (3) $1 : 2$ (4) $2 : 1$ 29. $A hot liquid is kept in a big room. According to Newton's law of cooling rate of cooling of liquid (represented as y) is plotted against its temperature T. Which of the following curves may represent the plot?$ (1) (2) (3) (4) 30. $Solar radiation emitted by sun resembles that emitted by a black body at a temperature of 6000 K. Maximum intensity is emitted at a wavelength of about 4800Å. If the sun were to cool down from 6000 K to 3000 K then the peak intensity would occur at a wavelength$ (1) $4800Å$ (2) $9600Å$ (3) $7200Å$ (4) $6400Å$