UPSC  Physics

1. Two sphere of the same material have radii 1 m and 4 m and temperature 4000 K and 2000 K respectively. the energy radiated per second by the first sphere is

Greater then by the second Less than that by the second Equal in both cases The information is incomplete to draw and conclusion

2. A surface at temperature T0 °K receives power P by radiation from a small sphere at temperature T >> T0 and at a distance d. if both T and d are doubled, the power received by surface will becomes approximately

P 2 P 4 P 16 P

3. If temperature of a black body increases from 7°C to 287°C, then the rate of energy radiation becomes

5 times 16 times 4 times 2 times

4. A bucket full of hot water is kept in a room and it cools from 75°C to 70°C in t1 minutes from 70°C to 65°C in t2 minutes and from 65°C to 60°C in t3 minutes; then

t1 - t2 = t3 t1 < t2 < t3 t1 > t2 > t3 t1 < t2 > t3

5. A body cools from 60°C to 50°C in 10 minutes. If the room temperature is 25°C and assuming newton’s law of cooling to hold good, the temperature of the body at the end of the next 10 minutes will be

38.5°C 40°C 42.85°C 45°C

6. Two spheres made of same material have radii in the ratio 2:1. if both the spheres are at same temperature, then what is the ratio of heat radiation energy emitted per second by them

1: 4 4: 1 3: 4 4: 3

7. 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 4800 A°. if the sun were cooled down from 6000 K to 3000 K, then the peak intensity would occur at a wavelength of

4800 A° 9600 A° 2400 A° 19200 A°

8. A person with dark skin as compared to a person with white skin will experience

Less heat and less cold More heat and more cold More heat and less cold Less heat and more col

9. Unit of distance used in navigation is

Nautical mile Kilometre Light year Yard

10. Match the columns:
List I List II
Forms Quantities
A. Cu sec 1. Pressure
B. Byte 2. Intensity of earthquakes
C. Richter 3. Rate of flow
D. Bar 4. Computer memory

4 1 2 3 2 4 3 1 3 4 2 1 3 2 1 4


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