How Does Electron Transfer Affect Human Net Charge?

[123yt]

Homework Statement

Human tissue contains about 3·10^27 electrons per kg of material. Suppose two humans each have a mass of 50 kg. We now transfer 0.0005 % of the electrons from the male human to the female. What are the net charges of the two humans afterwards?

Homework Equations

1 electron = 1.602 * 10^-19 Coulombs

The Attempt at a Solution

Took number of electrons per kg of material and multiplied it by the mass of the humans. Then, multiplied the male human's electrons by 0.999995 and the female human's electrons by 1.000005 to find the total amount of electrons on each person after the transfer. Then, multiplied both number of electrons by 1.602*10^-19 to find the charge.

 

[Beaker87]

The Attempt at a Solution

Took number of electrons per kg of material and multiplied it by the mass of the humans. Then, multiplied the male human's electrons by 0.999995 and the female human's electrons by 1.000005 to find the total amount of electrons on each person after the transfer. Then, multiplied both number of electrons by 1.602*10^-19 to find the charge.

This would be correct if neither person had any protons.

The problem does not specify, but I think it is reasonable to assume that both people started neutrally charged.
In order to solve this problem, don't think about how many total electrons each person has after the transfer, try to think how many EXTRA or MISSING electrons each person has; from there, you can solve how much extra or missing negative charge each person has.

 

[gneill]

What are the net charges on the humans before the transfer?

 

[123yt]

Tried assuming the people were neutral before the electron transfer:

Number of electrons per kg * Mass of a human = Number of electrons on a human before transfer

Took that number, multiplied it by 0.000005 to get number of electrons transferred, which is the number of extra and missing electrons.

Multiplied that number by 1.602 * 10^-19 to get the positive and negative net charge on each person.

Got the correct answer. Thanks a lot guys.