Question

An irrigation system supplies water at a pressure of 0.5 MPa and flow rate of 5,000 liter per hour. If both the pump and motor are 100% efficient, what is the current required of a 220 volt service. Give your answer as a bare number in amps, with no units attached.

Answer 1

3.16 A

Step-by-step explanation:

The irrigation system has a motor which is used to drive the pump. The efficiency of the system is the ratio of the power output to power input. It is given as:

Efficiency = Power output / Power input

Given that efficiency = 100% = 1, flow rate = 5000 liter / hour = 0.00139 m³/s, pressure = 0.5 MPa = 0.5 * 10⁶ Pa, voltage = 220 V.

Power output = supply of the pump = flow rate * pressure

Power output = 695 W

Efficiency = Power output / Power input

1 = 695 / power input

Power input = 695 / 1

Power input = 695 W

Also, Power input = input of motor = voltage * current

Power input = voltage * current

695 = 220 * current

current = 695 / 220

current = 3.16 A