Energy conversion devices Knowledge-Based Practice

Questions

1. 1.

   A photovoltaic solar panel with a surface area of 2.5 m$^2$ receives solar radiation with an intensity of 800 W/m$^2$. If the panel delivers a useful electrical power output of 360 W, what is the efficiency of this energy conversion device?

   • A) 45%
   • B) 27%
   • C) 22%
   • D) 18%
2. 2.

   An electric launcher accelerates a 0.50 kg projectile from rest to a speed of 40 m/s. If this energy conversion device operates with an efficiency of 80%, how much electrical energy is supplied to the launcher?

   • A) 320 J
   • B) 400 J
   • C) 1000 J
   • D) 500 J
3. 3.

   An energy conversion device operates with an efficiency of 25%. If the device performs 150 J of useful work during an operation, how much energy is dissipated as waste heat?

   • A) 112.5 J
   • B) 200 J
   • C) 600 J
   • D) 450 J
4. 4.

   An energy conversion device receives 800 J of total input energy and dissipates 280 J as waste heat to the surroundings. What is the efficiency of this device?

   • A) 35%
   • B) 48%
   • C) 54%
   • D) 65%
5. 5.

   A heat engine consumes fuel providing 180 kJ of chemical energy every minute. If the engine operates with an efficiency of 30%, what is its useful mechanical power output?

   • A) 54 W
   • B) 600 W
   • C) 900 W
   • D) 3000 W
6. 6.

   An electric crane with an efficiency of 80% is supplied with an electrical power of 4.0 kW. How long does it take for the crane to perform 96 kJ of useful mechanical work?

   • A) 24 s
   • B) 30 s
   • C) 40 s
   • D) 120 s
7. 7.

   An energy conversion system consists of an electric generator with an efficiency of 80% that powers a water pump with an efficiency of 70%. If a mechanical power of 5.0 kW is supplied to the generator, what is the useful power output delivered by the pump?

   • A) 2.8 kW
   • B) 3.5 kW
   • C) 3.75 kW
   • D) 2.5 kW
8. 8.

   An electric immersion heater with an efficiency of 75% delivers 180 kJ of useful thermal energy to a container of liquid in 2.0 minutes. What is the electrical power supplied to this heating device?

   • A) 1.1 kW
   • B) 1.5 kW
   • C) 1.8 kW
   • D) 2.0 kW
9. 9.

   An electric generator delivers a useful electrical power output of 3.6 kW while operating with an efficiency of 80%. What is the rate at which energy is dissipated as waste power by this energy conversion device?

   • A) 900 W
   • B) 720 W
   • C) 2880 W
   • D) 4500 W
10. 10.

    An electric motor draws 500 W of electrical power to lift a 20 kg load vertically at a constant speed of 1.5 m/s. Assuming $g = 10\text{ m/s}^2$, what is the efficiency of this energy conversion device?

    • A) 25%
    • B) 40%
    • C) 50%
    • D) 60%

Answers and step-by-step solutions appear after you finish the test.