Why do sparks radiate photons?

[Jonsson]

Hello there,

I am an undergrad physics student.

Electric sparks are used to ignite fuel. However, why do electric sparks release more heat than electricity conducted through a wire?

And what influences the amount of heat radiated from an electric spark? Why do some sparks radiate a lot of energy, whilst others do not? Is this only proportional to the electric current? Or are there other factors involved?

Thank you for your time.

Kind regards,
Marius

 

[sophiecentaur]

A spark can have a very short lifetime and there is very little 'mass' involved. This means you get a very high temperature. If you wanted to do the same thing with a 'resistor', it wouldn't last very long - for instance an automotive spark plug has a really tough life and the highly stressed component (the gas between the electrodes) is replaced every time the spark fires.

If you think about the arc that's used in welding, there is also a lot of energy dissipated in the supply leads and transformer, despite the fact that very thick wire is used. (Isquared R losses)