# Poisson Version 4

(BETA)

Demo Script
(click-drag the dielectric)

Reset

Poisson v4.0  requires a Java 1.1 enabled browser that allows JavaScript to applet communication.

Poisson calculates electrostatic potentials by numerically solving Poisson's equation in the presence of spherical and rectangular conductors, charge densities, and dielectrics.  The gradient of this potential is then calculated in order to display the electric field and the divergence is calculated to display the induced charge. Although Poisson may be used in interactive mode using a click and drag metaphor, it is designed to be scripted.  Many options, such as dielectrics, are only available through script.

Poisson is free for non-commercial educational use as outlined in the conditions of use.  It was written by  Wolfgang Christian.

## A new method called addObject has been added in version 4.0.

Almost all Physlets support one or more add methods designed to create an object and add it to the applet.  These objects usually, but not always, have an on-screen representation.  The addObject method, introducted in version 4, uses a naming convention adopted by other version 4 Physlets.

id=document.physletname.addObject(String name, String list)

The first argument is the name of the object to be added and the second is a comma-delimited list of parameters.  For example, both Animator, EField, and Poisson support addCircle methods that are invoked using the following JavaScript statements

id=document.physletname.addObject ("circle", "x = 0, y = -1.0, r = 10");

The new method is very forgiving since not all parameters need be specified. The default values are overridden only if they appear in the list.   Incorrect or unsupported parameters have no effect and are ignored.

Use the addObject method to create conductors, charge distributions, and dielectrics.

 Name Parameters chargedensity circle The object will be a circle if this parameter is present. x- double The x position of the base in world units y- double The y position of the base in world units. h- int The height in pixels. r- int The radius if the object is a circle. q- double The charge density. Returns the integer identifier of the object. conductor circle The object will be a circle if this parameter is present. x- double The x position of the base in world units y- double The y position of the base in world units. h- int The height in pixels. r- int The radius if the object is a circle. v- int The voltage. Returns the integer identifier of the object. dielectric circle The object will be a circle if this parameter is present. x- double The x position of the base in world units y- double The y position of the base in world units. h- int The height in pixels. r- int The radius if the object is a circle. chi- double The dielectric constant. Returns the integer identifier of the object.

The table below lists geometric shapes that can be added to Poisson.  Consult the on-line documentation for information about other methods.

 Name Parameters arrow x- double The x position of the base in world units y- double The y position of the base in world units. h- string The horizontal component as a function of t, x, y, vx, vy, ax, and ay. v- string The vertical component as a function of t, x, y, vx, vy, ax, and ay. box x- double The x position of the center in world units y- double The y position of the center in world units. h- int The height in pixels. w- int The width in pixels. circle x- double The x position of the center in world units y- double The y position of the center in world units. r- int The radius in pixels. caption text- string The text of the caption calc- string A function of t to be evaluated at every time step.  The value of the function is displayed to the right of the text. charge x- double The x position of the center in world units y- double The y position of the center in world units. q- double The object's charge. r- int The radius in pixels. connectorline id1- int The first object identifier. id2- int The second object identifier. cursor x- double The x position of the center in world units y- double The y position of the center in world units. r- int The radius in pixels. rectangle x- double The x position of the center in world units y- double The y position of the center in world units. h- int The height in pixels. w- int The width in pixels. shell x- double The x position of the center in world units y- double The y position of the center in world units. r- int The radius in pixels. text x- double The x position of the left side of the text in world units y- double The y position of the top of the text in world units. text- string The static text. calc- string A function of t, x, y, vx, vy, ax, and ay to be evaluated at every time step.  The value of the function is displayed to the right of the static text.