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# Hello, Any help on this would be very appreciated. I need help with 'C'

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An electric motor drives a pump that raises 0.15m3 of water per minute through a vertical height of 35m. Calculate:

A) the power required: 858.37W

B) the power required to drive the pump if it has an efficiency of 72%: 618.03W

C) the line current if the supply voltage to the motor is 220 volts DC:

Mar 30, 2021

#1
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If you did the first parts A and B correctly

know that   electricl watts =   V * I        where v = volts    I = current

858.37 w = 220 v   * I

I = 3.9 amperes

B)   If answer A is correct , this should be   858.37/.72 = 1192.2 watts

1192.2 watts = 220 v * I

I = 5.42 amperes

See this question for methodology to check your  'A' answer:

https://web2.0calc.com/questions/any-help-would-be-appreciated-thank-you_1

Mar 30, 2021
#2
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It appears you have "A'" correct

B) if the pump is 72 % efficient....it wastes 28% of the power supplied to it to pump the water ( friction/heat noise vibration etc)

.72 x  = 858.37

x = power required = 858.37/.72 = 1192.2 watts required         if 28% is wasted

ElectricPavlov  Mar 30, 2021
#3
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Should I show both values for current in my answer or should I pick just one? And thank you for your help.

I have revised my answer for "B"

TrainingSparky  Mar 30, 2021
edited by TrainingSparky  Mar 30, 2021
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I have no idea which current the question is asking about......I assumed both since it did not specify.....

ElectricPavlov  Mar 30, 2021