1. The problem statement, all variables and given/known data The electric potential difference across a neuron cell membrane is 0.070 V. The thickness of the membrane is 5.0 x 10-9 m. a) Find the magnitude of the electric field across the membrane. Describe any assumptions you are making. 2. Relevant equations ε = V/r 3. The attempt at a solution ε = 0.070V/5.0 x 10-9m = 1.4 x 107 N/C Assuming the width of the cell membrane is constant and that the electric field across it is uniform, the magnitude of the electric field is 1.4 x 107 N/C.