# Thread: magnitude of eletric field.

1. ## magnitude of eletric field.

The inner and outer surfaces of a cell membrane carry a negative and positive charge, respectively. Because of these charges, a potential difference of about 0.060 V exists across the membrane.

The thickness of the membrane is 9.00 x 10^-9 m. What is the magnitude of the electric field in the membrane?
in V/m

i believe the equation to be: E = V/r

not sure why .060V / 9.00 x 10^-9 would not work???

thanks for any help.

2. Originally Posted by rcmango
The inner and outer surfaces of a cell membrane carry a negative and positive charge, respectively. Because of these charges, a potential difference of about 0.060 V exists across the membrane.

The thickness of the membrane is 9.00 x 10^-9 m. What is the magnitude of the electric field in the membrane?
in V/m

i believe the equation to be: E = V/r

not sure why .060V / 9.00 x 10^-9 would not work???

thanks for any help.
I don't know why it doesn't work either. The space between the cell membranes work essentially like a capacitor, and the space is thin enough that, to a good approximation, we may regard these membranes as the plates of a parallel plate capacitor, which means you are using the correct formula. (Though I'd use a "d" instead of an "r." An "r" sounds too much like the radius of something.)

-Dan

3. okay it does work, i was using a negative in my scientific notation for the answer.