Efficiency Knowledge-Based Download PDF

Questions

1. 1.

   Two machines, X and Y, each perform 1200 J of useful work. If Machine X operates with an efficiency of 40% and Machine Y operates with an efficiency of 60%, how much more total energy does Machine X consume than Machine Y?

   • A) 1000 J
   • B) 240 J
   • C) 1800 J
   • D) 2000 J
2. 2.

   An electric motor with an efficiency of 75% is supplied with 2000 W of electrical power. How long does it take for the motor to perform 120,000 J of useful work?

   • A) 45 s
   • B) 60 s
   • C) 240 s
   • D) 80 s
3. 3.

   An industrial machine has an efficiency of 20% and wastes 2400 J of energy as heat during a cycle. What is the total energy input supplied to the machine?

   • A) 480 J
   • B) 1920 J
   • C) 12,000 J
   • D) 3000 J
4. 4.

   An electric winch supplied with 4000 W of electrical power lifts a 600 N load vertically through a height of 20 m in 4.0 s. What is the efficiency of the winch?

   • A) 60%
   • B) 75%
   • C) 80%
   • D) 85%
5. 5.

   A generator produces 480 J of useful electrical energy while wasting 120 J of thermal energy. What is the efficiency of the generator?

   • A) 80%
   • B) 75%
   • C) 25%
   • D) 20%
6. 6.

   A conveyor belt motor is supplied with 60 kW of electrical power and operates with an efficiency of 85%. What is the useful power output of the motor?

   • A) 9 kW
   • B) 51 kW
   • C) 69 kW
   • D) 71 kW
7. 7.

   A mechanical hoist with an efficiency of 60% performs 18,000 J of useful work while lifting a load. How much energy is wasted during this process?

   • A) 10,800 J
   • B) 12,000 J
   • C) 27,000 J
   • D) 30,000 J
8. 8.

   A water pump operates with an efficiency of 75% while delivering 1500 W of useful power. What is the total power input supplied to the pump?

   • A) 2000 W
   • B) 1125 W
   • C) 2625 W
   • D) 1875 W
9. 9.

   An electric motor operates with an efficiency of 40% while consuming 500 W of electrical power. At what rate is energy wasted by this motor?

   • A) 125 W
   • B) 200 W
   • C) 300 W
   • D) 700 W
10. 10.

    An electric motor consumes 800 J of electrical energy to lift a load, performing 600 J of useful mechanical work in the process. What is the efficiency of this motor?

    • A) 25%
    • B) 60%
    • C) 75%
    • D) 133%