Energy conversion devices Transitional Reasoning Practice
10 Physics practice questions on Energy conversion devices. Questions that build towards applied reasoning.
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Questions
- 1.
An off-grid environmental monitoring station uses a rooftop solar photovoltaic array with an effective surface area of 20 m² to harvest solar radiation. When the incoming solar irradiance is 750 W/m², the photovoltaic cells convert radiant energy into electricity with an overall efficiency of 16%. What are the electrical power output generated by the array and the total electrical energy it supplies during 5.0 hours of steady sunlight?
- 2.
A flywheel energy storage unit functions as an energy conversion device, using an integrated electrical machine to convert electrical energy into rotational kinetic energy during charging and back into electricity during discharge. During a charge phase, the unit draws a steady electrical power of 5.0 kW for 20 minutes to store 4.8 MJ of rotational kinetic energy in the rotor. In the subsequent discharge phase, the stored kinetic energy is converted back into electrical energy with a conversion efficiency of 90% to supply an emergency circuit. What are the energy conversion efficiency of the charging phase and the total electrical energy delivered to the emergency circuit?
- 3.
A motorized cable puller serves as an energy conversion device on an assembly line, pulling heavy components along a horizontal track at a constant speed of 1.5 m/s. The device draws a steady electrical input power of 3.0 kW and converts electrical energy into mechanical work with an efficiency of 80%. What is the magnitude of the horizontal pulling force exerted by the device, and how much energy is dissipated as waste heat during 45 seconds of continuous operation?
- 4.
An acoustic testing laboratory uses an electrodynamic loudspeaker as an energy conversion device to produce controlled sound waves. When operating at an electrical input power of 250 W, the loudspeaker transforms electrical energy into acoustic energy with a conversion efficiency of 4.0%, while the remaining power is dissipated as thermal energy in the voice coil. What is the useful acoustic power output generated by the loudspeaker, and how much thermal energy is dissipated in the device during 10 minutes of continuous operation?
- 5.
A geothermal thermoelectric generator extracts thermal power from underground hot brine at a constant rate of 50 kW and converts it into electricity, initially producing 6.0 kW of electrical power while rejecting the rest to a cooling loop. Engineers implement an improved semiconductor module that increases the device's overall conversion efficiency by an absolute 4 percentage points under the same thermal input. What are the new electrical output power produced by the generator and the new rate of heat rejected to the cooling loop?
- 6.
An electric delivery van cruises at a steady speed of 25 m/s along a straight, horizontal road against a constant total resistive force of 800 N. The vehicle's electric motor acts as an energy conversion device, transforming electrical energy stored in the battery pack into mechanical work with an efficiency of 80%. What is the electrical power drawn from the battery pack, and how much electrical energy is consumed from the battery during a 20-minute trip under these conditions?
- 7.
An emergency backup generator consumes fuel containing 180 MJ of chemical energy over a continuous operating period of 2.0 hours. Throughout this time, the device delivers a steady electrical power output of 7.5 kW to power critical facility circuits. What are the overall energy conversion efficiency of the generator and the average rate at which energy is dissipated as waste to the surroundings?
- 8.
A hybrid vehicle utilizes a regenerative braking device to capture mechanical kinetic energy and convert it into electrical energy stored in its battery pack during deceleration. While coming to a complete stop from an initial speed of 20 m/s in 8.0 s, the 1200 kg vehicle transfers energy to the battery pack with a conversion efficiency of 65%. Assuming all non-recovered energy is dissipated as thermal energy to the surroundings, what are the average electrical power delivered to the battery pack and the total thermal energy dissipated during this braking period?
- 9.
An industrial manufacturing unit uses an electric motor coupled to a hydraulic press to compress recycled composite panels. The electric motor draws 4.0 kW of electrical power and converts it into mechanical power with an efficiency of 90%, which then drives the hydraulic pump operating at an efficiency of 75% to perform useful work. What is the overall efficiency of this two-stage energy conversion device, and how much useful work does it perform on the panels during a 30-second operating cycle?
- 10.
An electric hoist converts electrical energy into gravitational potential energy to lift construction supplies. While operating at a constant electrical input power of 2.0 kW, the hoist lifts a 360 kg container vertically through a height of 15 m in 45 s at a steady speed. Taking the acceleration due to gravity as 10 m/s², what are the energy conversion efficiency of the hoist and the rate at which energy is dissipated to the surroundings?
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