# Question 7ab52

Jul 10, 2017

$1.14 \times {10}^{-} 18 \text{ kg}$

#### Explanation:

The polythene, after rubbing against the wool, gains a negative charge due to the transfer of electrons while the wool has lost electrons and has become positive in nature. To figure out the gain of the number of electrons on the polythene, we can do the following knowing that:

color(white)(--)color(blue)["1 electron has a charge of "-1.60xx10^-19" Coulombs"

• $\left(- 2 \times {10}^{-} 7 \cancel{\text{ C")/(1)*("1 electron")/(-1.60xx10^-19cancel" C}}\right)$
• $1.25 \times {10}^{12} \text{electrons}$

Now electrons do have a mass, although a small one. We calculate the amount of mass transferred as follows knowing that:

color(white)(----)color(blue)["1 electron has a mass of "9.11xx10^-31" kg"

• $\left(1.25 \times {10}^{12} \cancel{\text{electrons")/(1)*(9.11xx10^-31" kg")/(1 cancel"electron}}\right)$
• color(orange)[1.14xx10^-18" kg"#

$\text{Answer":color(orange)[1.14xx10^-18" kg}$