# The overall efficiency of a centrifugal pump is:

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The overall efficiency of a centrifugal pump is:

1. Product of manometric and mechanical efficiencies
2. Ratio of manometric efficient to mechanical efficiency
3. Product of manometric and hydraulic efficiencies
4. Ratio of mechanical efficiency to manometric efficiency

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Correct Answer - Option 1 : Product of manometric and mechanical efficiencies

Explanation:

In the case of a centrifugal pump, the power is decreasing from the shaft of the pump to the impeller and then from the impeller to the water. The following are the important efficiencies of a centrifugal pump:

1. Manometric Efficiency (ηman): It is the ratio of the manometric head to head imparted by the impeller to the water.

${\eta _{man}} = \frac{{{H_m}}}{{\frac{{{V_{w2}}{u_2}}}{g}}} = \frac{{g{H_m}}}{{{V_{w2}}{u_2}}}$

1. Mechanical Efficiency (ηm): It is the ratio of the power available at the impeller to the power at the shaft of the centrifugal pump.

${\eta _m} = \frac{{{\rm{Power\;at\;the\;impeller}}}}{{{\rm{Power\;at\;the\;shaft}}}} = \frac{{\frac{W}{g}\left( {\frac{{{V_{w2}}{u_2}}}{{1000}}} \right)}}{{{\rm{SP}}}}$

1. Overall Efficiency (ηo): It is defined as a ratio of the power output of the pump to the power input to the pump.
η= ηman × ηm