Two point charges of equal magnitude are 2.6cm apart. At the midpoint of the line connecting them, their combined electric field has a magnitude of 114NC. Find the magnitudes of the two charges.
(NOTE: Enter your answer in picocoulombs, pC.)
When solving for we divided the distance by two since we are concerned about the mid-point. We multiply by two since we have two charges.
Four point charges, each of magnitude are located at the corners of a square with sides of length . Two of the charges are +q, and two are −q. The charges are arranged in the following way: (1) the charges alternate in sign (+q,−q,+q,−q) as you go around the square; (2) the top two corners of the square have positive charges (+q,+q), and the bottom two corners have negative charges (−q,−q).
(a) In which configuration of the charges will the electric field at the center of the square have the greatest magnitude?
- Configuration 1
- Configuration 2
Explain: The charges cancel out in configuation 1.
(b) Calculate the magnitude of electric field at the center of the square for the first case:
And now for the second case:
(a) The cell membrane in a nerve cell has a thickness of 0.15μm. Approximating the cell membrane as a parallel-plate capacitor with a surface charge density of , find the electric field within the membrane.
When a nerve impulse propagates along a nerve cell, the electric field within the cell membrane changes from NC in one direction to NC in the other direction. Approximating the cell membrane as a parallel-plate capacitor, find the magnitude of the change in charge density on the walls on the cell membrane. Calculate your answer in units of C/m^2, and be sure to enter these units as part of your answer (REQUIRED).