Podcast
Questions and Answers
A cyclist is riding uphill. As they pedal, their muscles use chemical energy to move the bike upwards. Which of the following statements BEST describes the energy transfers and stores involved in this process?
A cyclist is riding uphill. As they pedal, their muscles use chemical energy to move the bike upwards. Which of the following statements BEST describes the energy transfers and stores involved in this process?
- Gravitational potential energy is converted into chemical energy as the cyclist moves uphill, requiring continuous input of kinetic energy to maintain motion.
- Chemical energy in the cyclist's muscles is directly converted into gravitational potential energy of the bicycle and cyclist system, with no other energy stores involved.
- Kinetic energy of the bicycle is directly converted into chemical energy in the cyclist's muscles, allowing them to move uphill while simultaneously storing energy.
- Chemical energy in the cyclist's muscles is transferred to kinetic energy of the cyclist and bicycle, which is then transferred to gravitational potential energy as they move uphill. Some energy is also transferred to thermal energy due to friction. (correct)
Infrared radiation from a hot oven transfers energy to its surroundings. Which type of energy transfer is primarily responsible for this?
Infrared radiation from a hot oven transfers energy to its surroundings. Which type of energy transfer is primarily responsible for this?
- Energy transfer by mechanical work, as the oven expands and contracts due to temperature changes.
- Energy transfer by heating, specifically through electromagnetic waves carrying thermal energy. (correct)
- Energy transfer by electric current, as the heating element inside the oven uses electricity.
- Energy transfer by a force moving an object, specifically the movement of air molecules heated by the oven.
A Sankey diagram is used to visually represent energy transfers in a system. What is the MOST significant feature of a Sankey diagram that makes it useful for analyzing energy efficiency?
A Sankey diagram is used to visually represent energy transfers in a system. What is the MOST significant feature of a Sankey diagram that makes it useful for analyzing energy efficiency?
- The arrows are drawn to scale, with the width of each arrow proportional to the amount of energy transferred through that pathway. (correct)
- The diagram always starts with multiple arrows converging into a single arrow, showing energy inputs combining.
- The inclusion of detailed labels for each energy store, providing a comprehensive textual description of the energy transformations.
- The use of different colors to represent different forms of energy stores, making it easy to distinguish between them.
Flashcards
Energy
Energy
The capacity for doing work. It exists in different stores and can be transferred but not created or destroyed.
Energy store
Energy store
The different ways in which energy can be stored, such as chemical, kinetic, gravitational potential, elastic potential, and thermal.
Energy transfer
Energy transfer
The ways energy moves from one store to another, including heating, waves, electric current, or a force moving an object.
Study Notes
- Energy exists in different 'stores'.
- Energy cannot be created or destroyed.
- Energy can be transferred, dissipated, or stored.
- Energy can remain in the same store for millions of years or a fraction of a second.
- Energy transfers occur constantly when a system changes.
Examples of Energy Transfers
- A boat moving through water transfers chemical energy into kinetic energy.
- Boiling water in an electric kettle involves electricity increasing the internal energy of the element.
- This increases the internal (thermal) energy of the water, raising its temperature.
- A swinging pirate ship ride transfers kinetic energy into gravitational potential energy.
Four Types of Energy Transfer
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Heating
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By waves
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Electric current
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By a force moving an object
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Potential difference (voltage) measures the energy given to charge carriers in a circuit, measured in volts (V).
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Voltage between two points causes electric current flow.
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Energy is 'given-out' by the material meaning the internal energy of the material decreases.
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Infrared radiation from the Sun emitted into space is an example of energy being 'given out'.
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Doing 'work' scientifically means energy has been transferred.
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Transfer diagrams show energy stores as boxes and energy transfers as arrows, illustrating how energy moves from one store to another.
Transfer Diagram Example (Child on a Slide)
- Gravitational energy stored in the child at the top of the slide transfers as mechanical work, increasing speed and working against friction.
- Energy shifts from gravitational potential energy to kinetic energy and internal energy, raising the temperature of the child and the slide.
Sankey Diagrams
- Start as one arrow splitting into multiple points, showing how energy in a system transfers into different stores.
- Useful for illustrating the amount of energy in each source.
- Arrow width is drawn to scale to represent the amount of energy.
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