When you hit a rock hard with a hammer, it produces electrical sparks. Where does that electricity comes?

Question

How can a spark flash just from a simple hit? Can someone explain that to me like I'm a 5 year old?

Answer 1

It is not likely that it is electrical - more likely it is thermal due to friction. A hammer hitting a rock concentrates alot of energy into the site of the impact. The energy gets dissipated in flying bits of rock (kinetic), and frictional heating when the rock and hammer slightly deflect.

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Answer 2

Few materials have that pronounced a piezoelectric effect. Instead, see the explanation in the reference. The kinetic energy of the hammer is concentrated on a tiny piece of the rock, which breaks off and is also heated by the impact. The 'spark' is a hot rock.

Answer 3

This is caused by something called the "piezoelectric effect." When compressed strongly enough, most minerals will generate electricity. Rocks are made of minerals, and a solid whack with a hammer sets off the piezoelectric effect. Just for the fun of it, get in a dark room with a mirror and chomp down on a lifesaver candy hard enough to break it. You'll see a tiny spark go off in your mouth. The piezoelectric effect at work!

Answer 4

Most solid items have different elements in them, some are sand and dirt, some are metallic in nature. Rocks have some metallic elements in them, therefore when a solid object strikes a rock, it will spark - especially when it does not break apart. Hopefully you weren't hitting a metallic object covered by sand and dirt too.