Podcast
Questions and Answers
Which of the following statements is true about energy?
Which of the following statements is true about energy?
- Energy can be both created and destroyed.
- Energy can be created but not destroyed.
- Energy can be destroyed but not created.
- Energy cannot be created or destroyed. (correct)
What is 'work' in the context of energy transfer?
What is 'work' in the context of energy transfer?
- A task done for employment.
- The energy that is destroyed.
- The energy stored in a system.
- The scientific way of saying that energy has been transferred. (correct)
What do the arrows in a transfer diagram represent?
What do the arrows in a transfer diagram represent?
- Energy stores
- The absence of energy
- The system
- Energy transfers (correct)
Flashcards
Energy
Energy
The capacity for doing work, existing in different 'stores.' It can be transferred, dissipated, or stored, but never created or destroyed.
System
System
An object or a group of objects considered as a whole for study. Changes within the system involve energy transfers.
Energy store
Energy store
The different ways in which energy can be stored, including chemical, kinetic, gravitational potential, elastic potential and thermal stores.
Study Notes
- Energy exists in different 'stores'.
- Energy cannot be created or destroyed.
- Energy can be transferred, dissipated, or stored.
- Calculation of energy changes can remain in the same store for millions of years or just a fraction of a second.
- Energy transfers occur continuously whenever a system changes.
- System denotes an object or a group of objects.
- Changing system results in changes to how some or all energy is stored.
- Examples of energy transfers include:
- A boat moving through water converts chemical energy to kinetic energy.
- An electric kettle converts electricity into internal (thermal) energy, increasing water temperature.
- A swinging pirate ship ride transfers kinetic energy into gravitational potential energy.
- Energy can be transferred via:
- Heating
- Waves
- Electric current
- A force moving an object.
- Potential difference (voltage) measures the energy given to charge carriers in a circuit, measured in volts (V).
- Voltage between two points enables electric current flow.
- Materials 'give out' energy resulting in decreased internal energy, like infrared radiation from the Sun.
- 'Work' refers to energy transfer, such as a cow grazing, a catapult firing, or a kettle boiling.
- Diagrams can illustrate energy transfer between stores, like transfer diagrams and Sankey diagrams.
- Transfer diagrams use boxes for energy stores and arrows for energy transfers.
- For a child on a slide, gravitational energy converts to kinetic and internal energy through mechanical work and friction.
- Gravitational potential energy shifts to kinetic energy and internal energy (raising the temperature of the child and the slide).
- Sankey diagrams start as one arrow splitting to show energy transfer into different stores, useful when energy amounts are known.
- Arrow width in Sankey diagrams represents the amount of energy, drawn to scale.
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