Question:Estimate how many electrons there are in your body. Make any assumptions you feel are necessary, but clearly state what they are. (Hint:Most of the atoms in your body have equal numbers of electrons, protons, and neutrons.) What is the combined charge of all these electrons?

Atoms are contained in cells and there are almost cells in a human body and each of them contain about 100 trillions atoms approximately.

$$\begin{gathered} {\text{N}}_{\text{cells}}{\text{=40×10}}^{12}\text{cell/humanbody} \\ {\text{N}}_{\text{cells}}{\text{=100×10}}^{12}\text{atoms/humanbody} \end{gathered}$$

Now, human body is made mostly of water 70% and the rest is assumedly carbon.

A water molecule as two hydrogen atoms that each contains one electron and one oxygen atom contains electrons. Carbon has in total electrons. So on an average, the number of electrons inside a human cell is,

$$\begin{gathered} N_{electrons}=\frac{1+6+8}{3} \\ =5 \end{gathered}$$

Thus, the total number of electrons in a human body is,

A single electron has the charge of,

$e=-1.6\times {10}^{-19}C$

Thus, the total charge of the electrons in a human body is,

Hence, the combined charges of all the electrons is $-3.9\times {10}^{9}C$.