Podcast
Questions and Answers
What is always true of energy?
What is always true of energy?
- It can be transferred between stores. (correct)
- It is destroyed in reactions.
- It is created in reactions.
- It is used up over time.
Which of the following is an example of energy transfer?
Which of the following is an example of energy transfer?
- A plant using sunlight to grow.
- A rock sitting still on the ground.
- A car parked on the side of the road.
- Water being heated in a kettle. (correct)
In a Sankey diagram, what do the widths of the arrows represent?
In a Sankey diagram, what do the widths of the arrows represent?
- The speed of the energy transfer.
- The efficiency of the energy transfer.
- The type of energy being transferred.
- The amount of energy transferred. (correct)
Flashcards
Energy
Energy
The capacity for doing work; it exists in different 'stores' and can be transferred, dissipated, or stored.
System (in Physics)
System (in Physics)
An object or group of objects where energy transfers occur. Whenever a system changes, so does the energy stored within it.
Energy Transfer Diagrams
Energy Transfer Diagrams
Diagrams that use arrows and boxes to show how energy is transferred from one store to another. Arrow width indicates the amount of energy transferred.
Study Notes
- Energy exists in different 'stores' and can be transferred, dissipated, or stored.
- Energy cannot be created or destroyed.
- Energy can remain in the same store for varying lengths of time.
- Energy transfers occur constantly whenever a system changes.
Examples of Energy Transfers
- A boat moving through water transfers chemical energy into kinetic energy.
- Heating water in an electric kettle involves electrical energy increasing the internal energy of the element, which in turn increases the internal (thermal) energy of the water.
- 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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Doing 'work' scientifically means energy has been transferred.
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Examples of doing work include a grazing cow, a firing catapult, and a boiling kettle.
Diagrams for Showing Energy Transfer
- Transfer diagrams use boxes to represent energy stores and arrows to represent energy transfers.
- Example: A child at the top of a slide transfers gravitational potential energy into kinetic energy and internal energy (raising the temperature of the child and the slide).
- Sankey diagrams start as one arrow that splits, showing how all energy in a system is transferred into different stores.
- The width of the arrow in a Sankey diagram is drawn to scale to represent the amount of energy.
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