78. If rw is the radius of the well pipe, R is the radius of influence and H is thickness of a confined aquifer, the ratio of the discharge of a well sunkqip to the top of the acquifer to the discharge of the well fully penetrated, is

A. 2.3 ? lo& 7?R ) H rw

B. z.o ? iogio ?Hrw

C. 2.3 ? logio i ?R wTIV

D. 2,3 H rw log10i ---?R )

79. In an artesian acquifer, the draw downs in two observation wells at distances 100 m, and 200 m were found same after one hour and x hours respectively. The value of x, is

A. 2 hours

B. 4 hours

C. 9 hours

D. 16 hours.

80. The depth of the water table at a place is 45 m below the general ground level. To lift water from a deep tube well in such a locality, the type of pump to be installed is

A. Centrifugal pump

B. Reciprocating pump

C. Deep well turbine pump

D. None of these.

81. The head against which the motor works for lifting water, is

A. maximum depth of water table below ground level

B. maximum depression head

C. velocity head

D. all the above.

82. The efficiency of a pumping set, is generally assumed

A.50%

B.55%

C.60%

D.65%

83. For 3.25 x 10-2 cumecs discharging from a well, a pump is installed to lift water against a total head of 30 m. The minimum required horse power, is

A. 10 H.P.

B. 15 H.P.

C._ 18 H.P.

D. 20 H.P.

84. Ground water from artesian wells

A. contains no suspended materials

B. contains dissolved salts

C. may be saltish and hard

D. all the above.

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