# Magnitude of the work done by electric field.

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1. Feb 14, 2017

### jlmccart03

1. The problem statement, all variables and given/known data
The membrane around a cell normally has layers of charge that create a potential difference between its outer and inner surfaces. This difference is about 72 mV .

When a singly ionized potassium ion moves through a channel in the membrane passing from the outside to the inside, what is the magnitude of the work done by the electric field of the membrane?

2. Relevant equations
W = F*d
W = V*U

3. The attempt at a solution
So I know that the charge of a K ion is +1 so it is simply 1.6e-19 and converting 72 mV to 0.072 V I can then just multiply both to get the change in work correct? I don't get why that is wrong then.

2. Feb 14, 2017

### Staff: Mentor

Just a multiplication error.
Quick check: If you multiply 1.6*10-19 by 0.072, the result should be smaller than 10-19.

3. Feb 14, 2017

### jlmccart03

Yeah I keep getting 1.15e-19. Isn't that correct, I cant seem to get a different answer on my calculator. Nevermind I got the answer. I was using -18 instead of -19.