Calculate input power from the data

In summary, an electric motor with an efficiency of 78% drives water pump. It is required of the motor (in kW) to pump 22250 gals of water from the lake to a storage tank 65 feet above the lake surface in 4 hours.
  • #1
asnali4u
5
0
An electric motor with an efficiency of 78% drives water pump. What input power is required of the motor (in kW) to pump 22250 gals of the water from the lake to a storage tank 65 feet above the lake surface in 4 hours?
Attempt :
i know that efficiency = output/input
but i don't understand, how to calculate the output through this data
 
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  • #2
We cannot assist without first seeing your attempt at a solution.
 
  • #3
Hint: Power is work done per unit time. Does that help?
 
  • #4
LawrenceC said:
Hint: Power is work done per unit time. Does that help?

Output = power = work/time
Here work will be force x distance?
To be honest i am not familiar with the unit "gal". My lecturer did not tell us about this.
 
  • #5
Gal is short for gallon. A gallon is exactly 231 in^3 in volume.
 
  • #6
LawrenceC said:
Gal is short for gallon. A gallon is exactly 231 in^3 in volume.


so how can i use volume or gal in the output equation?
 
  • #7
Gallons can be converted to cubic feet. Cubic feet of water can be converted to weight knowing the density of water in pounds/ft^3. If you know the weight and the height the water is lifted, you have the work done (ft-lbs). Factor in efficiency and time and come up with the answer you seek. You'll need to do some unit conversion to get to KW but that's easy.
 
  • #8
LawrenceC said:
Gallons can be converted to cubic feet. Cubic feet of water can be converted to weight knowing the density of water in pounds/ft^3. If you know the weight and the height the water is lifted, you have the work done (ft-lbs). Factor in efficiency and time and come up with the answer you seek. You'll need to do some unit conversion to get to KW but that's easy.

Thanks for the help. I will try this.
 

FAQ: Calculate input power from the data

What is input power and how is it calculated?

Input power refers to the amount of energy that is being supplied to a system or device. It is typically measured in watts (W) and can be calculated by multiplying the voltage (V) by the current (I) flowing through the system or device: P = VI.

How accurate are the calculations for input power?

The accuracy of input power calculations depends on the accuracy of the voltage and current measurements. If these measurements are precise, then the calculated input power will also be precise. However, external factors such as fluctuations in the power supply or variations in the electrical components can affect the accuracy of the calculations.

What is the significance of calculating input power?

Calculating input power is important in understanding the energy consumption and efficiency of a system or device. It can also help in identifying any potential issues or malfunctions within the system that could be causing a higher input power than expected.

Are there any limitations to calculating input power from the data?

One limitation to calculating input power from the data is that it does not take into account any losses or inefficiencies within the system. For a more accurate measurement of power consumption, other factors such as power factor and impedance must also be considered.

Can the input power be adjusted or controlled?

In most cases, the input power cannot be directly adjusted or controlled. However, by understanding the input power and its relationship to voltage and current, it is possible to make changes to the system or device to optimize its efficiency and reduce power consumption.

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