A steady brightness(Exposition)

Thinking carefully about a steadily glowing lamp

A lamp glowing steadily is shifting energy at a steady rate. In a simple circuit, where the wires connect one lamp to one cell, energy is being shifted to or from stores at two places: the lamp and the cell. The same change is calculated at both: energy is shifted from the chemical store associated with the cell, and to the thermal stores around the lamp. That the change is the same seems like too much of a coincidence for there not to be a strong connection, and, of course, there is. The wires make the physical connection (there is a similar connection in the energy description). The same electrical working empties the chemical store and fills the thermal stores. This is what electric circuits are good at: connecting stores so that we can arrange the rates of depletion and accumulation.

Electrical working is the pathway that empties the chemical store at a calculable number of joules/second or watts. Electrical working is also the pathway that fills the thermal stores at the same rate. This power in this pathway is a constant number of watts. It is the link between the stores.

Predicting the rate of shifting of energy, by an electrical pathway, comes next.

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 PN thread – connect all three threads from any link

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


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