Is it helpful to talk about electrical energy?(Challenge)



Electrical energy is an unhelpful phrase

Wrong Track: When the bulb is lit in the circuit, chemical energy from the cell is transferred to electrical energy in the wires, which is then transferred to heat and light energy in the bulb and surroundings.

Right Lines: When the bulb is lit in the circuit, energy is shifted from the chemical store associated with the cell to the thermal store of the surroundings.

How to be more helpful

Thinking about the learning

There are significant differences between these two ways of talking and thinking about simple electrical loops:

The right lines approach does not refer to different kinds of energy: chemical energy, electrical energy, heat and light energy. Here, energy is energy, and it's associated with different kinds of energy store.

The right lines approach has no place for electrical energy. Whereas energy can be stored in a cell (a chemical store of energy), it is difficult to see in what sense energy can be stored in the connecting wires of a circuit.

While the electrical circuit is clearly not a store of energy, it does provide the pathway along which energy is shifted by cell and bulb.

Taking the right lines approach, we therefore refer to electrical pathways but not to electrical stores.

Similarly, the right lines approach has no place for light energy. Light is taken to provide a pathway along which energy can be shifted but does not itself constitute an energy store. Taking the right lines approach, we therefore refer to light pathways but not to light stores.

Thinking about the teaching

We are clear that the right lines approach makes much more sense than the existing schemes, which refer to different kinds of energy including electrical energy and light energy. At the same time we recognise that changing to this approach involves the big challenge of changing familiar routines for both students and teachers.

The story of the circuit loop that we're moving towards is based on chemical and thermal stores and two linked pathways (electrical and heating), which operate simultaneously:

When the circuit loop is complete, a current circulates and the bulb glows.

When the bulb is glowing, energy is being shifted along an electrical pathway from the chemical store associated with the cell to the thermal store associated with the bulb (only whilst the bulb is first warming up) and to the thermal store associated with the surroundings. The circuit elements associated with the electrical pathway consist of the cell (providing a potential difference), connecting wires and bulb (offering resistance).

Electrical working occurs as charge passes through the resistance of the bulb, and energy is shifted with the chemical store being depleted and the thermal store associated with the bulb being filled.

The glowing bulb heats the surroundings through thermal conduction, convection and radiation.

The glowing bulb shifts energy to the surroundings along two pathways: heating by particles (through conduction and convection) and heating by radiation (both through emitted light and non-visible radiations).

Overall the energy level of the chemical store of the cell goes down as the energy level of the thermal store of the surroundings goes up. The power in the pathways into and out of the bulb is the same.



Prepare for teaching across the topic using these links

topic kitset topic path core ideas (topic) decisions to make (topic) suggestions (for the topic) topic issues



This is a nugget in the TL thread – connect all three threads from any link

Physics Narrative (PN) Teaching & Learning Issues(TL) Teaching Approaches(TA)

<< >>



SPT and IoP Logo

privacy link