A 80mmdiameter copper ball is charged to 70 Nc What fraction

A 8.0-mm-diameter copper ball is charged to 70 Nc. What fraction of its electrons have been removed? The density of copper is 8900 kg/m3.

Solution

Here,

diameter of copper , d = 8 mm

radius ,r = 8/2 = 4 mm

charge , q = 70 nC

number of electrons removed = q/e

number of electrons removed = 70 *10^-9/(1.602 *10^-19)

number of electrons removed = 4.369 *10^11

Now , for total number of electron

total number of electrons = 4pi/3 * (0.004)^3 * 8900 * 10^3/63.5 * 6.022 *10^23 * 29

total number of electrons = 6.56 *10^23

fraction of electrons removed = number of electrons removed/total number of electrons

fraction of electrons removed = (4.369 *10^11)/(6.56 *10^23)

fraction of electrons removed = 6.66 * 10^-13

fraction of its electrons have been removed is 6.66 * 10^-13