What must the charge (sign and magnitude) of a 1.70 gg particle be for it to remain balanced against gravity when placed in a downward-directed electric field of magnitude 640 N/CN/C ? Express your answer in coulombs.

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.