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
 B.    Battery              2.   Mechanical energy
                                 into Electrical
 C.    Washing Machine      3.   Chemical energy
                                 into electrical
 D.    Dynamo               4.   Electrical energy
                                 into chemical
            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)