[SOLVED] magnitude of electric field. 1. The problem statement, all variables and given/known data 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 .060 / 9.00 x 10^-9 would not work??? 2. Relevant equations 3. The attempt at a solution it says my answer of: 6.7E-6 is incorrect??