NTA Abhyas JEE Main2020PhysicsWork, Power and EnergyPractice
An installation consists of an electric motor which drives a water pump to lift 75 L of water per second to a height of 5 m , where water is disbursed at negligible speed. If the motor consumes a power of 5 kW , then what is the efficiency (%) of the installation? [ g = 10 m s - 2 ]
Correct answer
75
Step-by-step solution
Power consumed by the motor P motor = 5000   W Power used in lifting the water P water = mgh t = 75 × 10 × 5 1 = 3750   W The efficiency of the motor is η = P water P motor × 100 % η = 3750 5000 × 100 % = 75 %