there are 2 probs here. 1) 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 0.0680 V exists across the membrane. The thickness of the membrane is 7.95×10-9 m. What is the magnitude of the electric field in the membrane? I thought i could just use E=-change in V/change in distance, but no. 2) Two hollow metal spheres are concentric with each other. The inner sphere has a radius of 0.1440 m and a potential of 86.0 V. The radius of the outer sphere is 0.146 m and its potential is 82.0 V. If the region between the spheres is filled with Teflon, find the electric energy contained in this space. This one i played with in the equation V=(kq/rsquared)+(k/q'/rsquared). I've just confused myself with working them so many times. so im seeking help here!