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Various topics related to energy conversion devices and their efficiencies. It discusses the principles of energy conversion, including the first law of thermodynamics, the concept of efficiency, and the differences in efficiency between various devices like power plants, electric motors, and light bulbs. The document also explores the primary forms of useful energy output for different devices, such as mechanical energy for cars, radiation for computer screens, and heat for heat engines. Additionally, it covers the calculation of carnot efficiency and overall system efficiency. A comprehensive understanding of energy conversion and efficiency, which are crucial concepts in fields like engineering, physics, and energy studies.
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Which one of the following is true about energy conversion devices?
Total Energy Input = Useful Energy Output + Energy Dissipated to the surroundings
Total Energy Input = Useful Energy Output
Typically a power plant has an efficiency of 35%, and an electric motor an efficiency of 90%. An incandescent electric bulb has an efficiency of 5% and fluorescent light bulbs have an efficiency of about 20%. Refer to section 3.3: Typical Efficiencies of Day to Day Devices.
Light bulb
Electric motor
Power plant
Which one of the following devices is least energy efficient? (1 point)
What is the form of useful energy output in the case of a computer screen?
Total Energy Input = Energy Dissipated to the surroundings
Total Energy Input = Efficiency X Total Energy Output
Total energy = useful energy + waste energy. Refer to section 3.2: Energy Conversion Devices.
First law of thermodynamics states that Energy output must be equal to the input. It cannot be created.
False
True
Energy can be created when we burn fossil fuels. (1 point)
A heat engine converts thermal energy into what type of energy?
What is the form of useful energy output in the case of a TV?
Radiation
Mechanical
Thermal or Heat
Chemical
A TV converts electrical energy into radiation (the pictures that we see). Refer to section 3.2: Energy Conversion Devices.
Most energy conversion processes produce heat as a by product. Refer to section 3.2: Energy Conversion Devices.
Motion
Sound
Heat
Light
What is the most common by product of fossil fuel-based energy conversion processes?
Mechanical
Thermal
Chemical
Electrical
A heat engine is defined as a device that converts heat energy into mechanical energy.
Efficiency = ((useful energy output) / (useful energy output + waste energy output))*100. Note: Use units consistently. Please refer the section of the Efficiency of Energy Conversion Devices.
The useful output from a heat engine is 212 cal. The energy that is wasted is 4,235 J. What is the Carnot efficiency of the engine? (Answer with units of %. i.e. 30 not 0.3. you do not need to provide the %)
The following step efficiencies apply to the use of gasoline in a car: Crude production: 95.9%, Refining 80.5%, Transportation 93.4%, Engine efficiency 20%. What is the total efficiency of the process? (Answer units: %, i.e. input 10 not 0.1. Be sure to exclude the % as Canvas does not accept symbols)
Use the Carnot efficiency formula and temperatures in Kelvin. Please refer to section covering The Carnot Efficiency.
Quiz Score: 22 out of 25
Overall Efficiency of a system is the product of step efficiencies. Please refer to section 3.9: Calculating Overall Efficiency.
