Is it true that once rock forms it never changes

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

where is the circuit diagram ?

the higher the current the higher the mag field around it the higher the influence on the compass