Ans : (c)
79. Rise of mercury in a barometer indicates:
     (a) fair weather
     (b) storm
     (c) rain
     (d) Both (b) and (c)
Ans : (a)
80. A cup of hot tea on a metal table in a room loses heat by :
     (a) conduction and convection
     (b) conduction, convection, radiation and evaporation
     (c) conduction and evaporation
     (d) conduction and radiation
Ans : (b)
81. Match the following:
 A.    Battery charger      1.   Electrical energy
                                 into mechanical
                                 energy
 B.    Battery              2.   Mechanical energy
                                 into Electrical
                                 energy
 C.    Washing Machine      3.   Chemical energy
                                 into electrical
                                 energy
 D.    Dynamo               4.   Electrical energy
                                 into chemical
                                 energy
            A        B         C           D
       (a)  4        3         1           2
       (b)  4        3         2           1
       (c)  1        2         3           4
       (d)  3        4         1           2
Ans : (a)
82. The best and the poorest conductors of heat are respectively [NDA2010]
       (a) silver (Ag) and lead (Pb)
       (b) copper (Cu) and aluminium (AI)
       (c) silver (Ag) and golcl (Au)
       (d) copper (Cu) and gold (Au)
Ans : (a)
83. When light passes from air into glass it experiences change in :
       (a) frequency and wavelength
       (b) frequency and speed
       (c) wavelength and speed
       (d) frequency, wavelength and speed
Ans : (c)
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