Energy Transferred by Working
Energy and Thermal Physics

Confusing physical and energy perspectives

Teaching Guidance for 11-14 Supporting Physics Teaching

Describing energy shifts

Wrong Track: When I lift the book onto the shelf, chemical energy is transferred from my arm to gravitational potential energy in the book.

Right Lines: When I lift the book onto the shelf, energy is shifted from the chemical store of my arm to the gravitational store of the book.

Energy is not a substance

Thinking about the learning

Very often, pupils describe energy changes as if energy were a real substance that was taken out of one object, transformed into a different kind of energy and then put into another object. Such descriptions mix physical and energy descriptions. The orange fluid we suggest as a teaching model is a physical analogue of the energy description: it's not an assertion about real flows of tangible stuff.

Thinking about the teaching

Differentiating between lived-in-world, physical and tangible objects and energy stores helps to keep the two levels of description separate.

  • One level of description concerns the changes you can see and measure directly (lifting a book onto a table; throwing a ball at a wall). This involves the real, physical world.
  • The other level focuses on tracking changes in the amount of energy in the stores associated with real objects. This involves the abstract world of theory.

You'll need to be explicit about what you're up to in order to keep the two kinds of description separate.

Energy Transferred by Working
appears in the relation dU=dQ+dW
is used in analyses relating to Working Engines Thermionic Emission
is a special case of Work
has the special case Potential Energy Kinetic Energy

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