How is a spark created from scraping metal to start a fire?

[InsertName]

On a fundamental level, can anyone explain how a spark is created from scraping a knife along a piece of metal as done by people who want to light fires 'in the wild'?

 

[LostConjugate]

Electrons are removed from the metal causing it to become charged, then a spark may occur even at such a low voltage because of the very small surface area at the edge of a knife.

 

[Drakkith]

Electrons are removed from the metal causing it to become charged, then a spark may occur even at such a low voltage because of the very small surface area at the edge of a knife.

I'm not sure this is correct. From wikipedia on Flint: When struck against steel, a flint edge will produce sparks. The hard flint edge shaves off a particle of the steel that, heated by the friction, reacts with oxygen from the atmosphere and can ignite the proper tinder.

I think a similar effect is happening between a knife and metal. It generates high friction which produces "sparks".

 

[DragonPetter]

I'm not sure this is correct. From wikipedia on Flint: When struck against steel, a flint edge will produce sparks. The hard flint edge shaves off a particle of the steel that, heated by the friction, reacts with oxygen from the atmosphere and can ignite the proper tinder.

I think a similar effect is happening between a knife and metal. It generates high friction which produces "sparks".

Yes, I think sparks are actually pieces of the metal heated by friction, and the temperature causes the metal embers to be incandescent.

I don't think it is an electrostatics phenomenon.

 

[InsertName]

Thank you.

 

[LostConjugate]

Then how can it be a spark?

 

[nasu]

"Spark" has (at least) two meanings.
One is a small incandescent particle.
If talking about a fire, "spark" means small incandescent particle (of carbon, usually).
The second meaning of "spark" refers to an electrical discharge.