Around 6 trillion electrons are added to an object when you charge it by rubbing it with a cloth.
You can calculate this value by knowing that the charge we can measure on such objects in the order of the microcoulomb, Q = 1 × 10-6 C. Apply the formula to calculate the number of excess electrons to find the number of particles:
n = Q/e = 1 × 10-6/1.602176634 × 10−19 = 6.2412 Read more