Podcast
Questions and Answers
What happens to the total energy supplied when a device operates at a certain efficiency?
What happens to the total energy supplied when a device operates at a certain efficiency?
When calculating payback time for energy-saving installations, which factor is NOT taken into consideration?
When calculating payback time for energy-saving installations, which factor is NOT taken into consideration?
In the context of efficiency, what is the significance of a Sankey diagram?
In the context of efficiency, what is the significance of a Sankey diagram?
Which of the following statements accurately describes the distinction between accuracy and precision in measurements?
Which of the following statements accurately describes the distinction between accuracy and precision in measurements?
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How is the efficiency of a kettle calculated based on the given data?
How is the efficiency of a kettle calculated based on the given data?
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Study Notes
Efficiency
- Efficiency is the percentage of useful energy transferred.
- The efficiency of a device is calculated using the formula: efficiency = (useful energy transferred / total energy supplied) x 100%.
- A Sankey diagram can be used to represent energy transfers.
- The width of each arrow in a Sankey diagram represents the amount of energy.
- In a kettle, energy is stored in the hot water, the kettle itself, and the surroundings. All three represent energy loss.
Paying for Energy
- We pay for the amount of energy we use.
- Energy companies measure energy consumption in kilowatt-hours (kWh).
- One kWh is the amount of energy transferred when a 1 kW appliance is used for one hour.
- Reducing energy bills can be achieved through insulation and using more efficient appliances.
- Payback time is the length of time it takes for savings from energy efficiency improvements to pay back the cost of the improvements.
- Payback time can be calculated using: payback time = cost of change / savings per year.
Accuracy & Precision
- Accuracy refers to how close a measurement is to the true value.
- Precision refers to how consistent measurements are.
- Measuring devices with smaller divisions allow for more accurate measurements than devices with larger divisions.
- Precise measurements may not be accurate if the measuring instrument is not set up correctly.
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Description
This quiz explores the concepts of energy efficiency, the calculation of useful energy transfer, and the financial aspects of energy consumption. You'll learn how to determine efficiency percentages, understand Sankey diagrams, and calculate payback times for energy-saving improvements. Test your knowledge on how we pay for energy and ways to reduce costs.
