Summary: Page 5 of 6 of a PLTL workshop on Coulomb law fields, for undergraduate physics.
Copyright © 2005, G. Raymond Brown, Ph.D.
Work on these problems with your Peer Team members. Determine analytic solutions before substituting any numerical values to find a numerical solution. Each problem is solved by use of either Equation 2 (
Consider a disk in the
Repeat Problem 1 with the charge density changed to
The figure below can be taken as a very crude model of a water molecule. The red disk represents the oxygen atom and the two green disks represent the hydrogen atoms in the water molecule. Given the coordinate system shown in the diagram, find the electric field everywhere on the
Isolated Water Molecule |
---|
Four equal point charges
Tetrahedron of Identical Point Charges |
---|
(a) Demonstrate that the electric field at the origin is zero.
Now consider the red spheres to represent hydrogen atoms, and add a nitrogen atom at the center of the tetrahedron (blue sphere). This gives us a (very, very crude) model of the ammonium ion,
Crudely Modeled Ammonium Ion |
---|
(b) For this model, consider a field point located at the center of any one of the four triangular sides of the tetrahedron. The sum for the electric field at this point reduces to contributions from only two of the five point source charges. Why? Which two charges sum to make a nonzero contribution? Is the direction of this electric field pointing out of the tetrahedron or into it? What is the value of the electric field at this field point? Justify your answers.