why can't sun heat produce fire rather than a small spark produced in an electrical switch

Question

when we do some kind electrical works (drilling) near highly flammable solvents we may find fire explosion. in the same case why can't sun heat produce fire rather than a small spark produced in an electrical switch ? I think this small spark has less temperature than that of sun heat/ please kindly help me

Answer 1

Some minimum temperature is required to start a chemical reaction.  In an explosion or a fire, the heat produced by that reaction is enough to keep it going as long as there is oxygen and fuel.  Flammable liquids evaporate, creating a cloud of vapor ready to burn if you can get the combustion started.

The temperature of objects heated by the sun is fairly low, typically below about 200 degrees on a hot day.

The temperate of an electric spark is from about 5000 degrees up.  It doesn't feel warm because it's tiny and only lasts for an instant.  While the total amount of heat from a spark in a switch is small, it's really concentrated and the temperature is very high.  Just that tiny spec of high temperature is enough to start the combustion of a flammable gas in air, and once started: BOOM.