WEST BENGAL JOINT ENTRANCE EXAMINATION,2011
Physics
( English Version )
Multiple Choice Question
(Each question carries one mark)
1. Two temperature scales A and B related by [tex]{{A - 42} \over {110}} = {{B - 72} \over {220}}[/tex]. At which temperature two scales have the same reading ?
A. -42° B. -72º C. +12° D. -40º
2. An ideal gas is compressed isothermally until its pressure is doubled and then allowed to expand adiabatically to regain its original volume ([tex]\gamma = 1.4[/tex] and 2–1.4 = 0.38). The ratio of the final to initial pressure is
A. 0.76 : 1 B. 1 : 1 C. 0.66 : 1 D. 0.86 : 1
3. Air inside a closed container is saturated with water vapour. The air pressure is p and the saturated vapour pressure of water is [tex]\overline p [/tex] . If the mixture is compressed to one half of its volume by maintaining temperature constant, the pressure becomes
A. 2(p +[tex]\overline p [/tex]) B. 2p +[tex]\overline p [/tex] C. (p+ [tex]\overline p [/tex])/ 2 D. p+2[tex]\overline p [/tex]
4. 1.56 × 105 J of heat is conducted through a 2m2 wall of 12 cm thick in one hour. Temperature difference between the two sides of the wall is 20°C. The thermal conductivity of the material of theWall is (inW m–1 K–1)
A. 0.11 B. 0.13 C. 0.15 D. 1.2
5. A diver at a depth of 12 m in water [tex]\mu = {4 \over 3}[/tex] sees the sky in a cone of semivertical angle
A. [tex]{\sin ^{ - 1}}\left( {{4 \over 3}} \right)[/tex] B. [tex]{\tan ^{ - 1}}\left( {{4 \over 3}} \right)[/tex] C. [tex]{\sin ^{ - 1}}\left( {{3 \over 4}} \right)[/tex] D. 90°
6. Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is
A. 9D B. 2D C. 3D D. 7ডি
7. A convex lens of focal length 20 cm produces 5 times magnified real image of an object. What is the object distance ?
A. 36 cm B. 25 cm C. 30 cm D. 150 cm
8. If the focal length of the eye piece of a telescope is doubled, its magnifying power (m) will be
A. 2 m B. 3 m C. m/2 D. 4 m
9. A plano-concave lens is made of glass of refractive index 1.5 and the radius of curvature of its curved face is 100 cm. What is the power of the lens ?
A. + 0.5 D B. –0.5 D C. –2 D D. +2D
10. Four charges equal to –Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium, the value of q is
A. [tex]{{ - Q} \over 4}\left( {1 + 2\sqrt 2 } \right)[/tex] B. [tex]{Q \over 4}\left( {1 + 2\sqrt 2 } \right)[/tex] C. [tex]{{ - Q} \over 2}\left( {1 + 2\sqrt 2 } \right)[/tex] D. [tex]{Q \over 2}\left( {1 + 2\sqrt 2 } \right)[/tex]
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