There isn't a clear single answer to this question because it depends on how you define "usable energy." However, one possible answer is:
Chemical energy becomes usable energy in a battery when electrons flow through a circuit, powering a device or doing work. This happens when the battery is connected to a load that creates a path for the electrons to flow from the battery's negative terminal to its positive terminal, known as the external circuit. Inside the battery, chemical reactions occur that convert stored chemical energy into electrical potential energy, which drives the electron flow. So, chemical energy becomes usable energy in a battery when electrons start moving between atoms, not when they stop moving.
In a battery when does chemical energy become usable energy?
when the current becomes zero
when a reaction produces the same products
when there is chemical reaction between metals and nonmetals
when electrons stop moving between atoms
1 answer