PowerPlot Documentation

To contact me:

Email: w@no_spam_allowed_wdell.com
Web site: wdell.com

This program is copyrighted by Walton Dell. You may not make any more copies than allowed by your software license agreement.

Program description:

This program displays electric fields due to positive charges. The charges are represented by red dots on the screen. You can click to place charges in any arrangement you wish. The density of the electric field vectors can be adjusted from a single vector to a very dense field. The charges can be animated, bouncing off the edges of the screen.

Program installation:

This program requires DirectX 5+. Install DirectX drivers if necessary. (Go to www.microsoft.com/directx/, then scroll down to "DirectX 5 for users", then find and download dx5eng.exe, then run that program.)

Extract Physics.exe from Physics.zip to a folder of your choice using a ZIP compression program (such as WinZip).

Now double-click Physics.exe to start the program.

Commands:

Escape	=	Exit program
1	=	Preset mode 1: Single test point, with one charge (the mouse).
2	=	Preset mode 2: Two charges (one is the mouse) in animation mode with electric field vectors.
3	=	Preset mode 3: "Symmetric" grid animation.
4	=	Preset mode 4: Constant force field.
5	=	Preset mode 5: "Springy" animation.
+	=	Add positive charge at random position (or click mouse!).
-	=	Remove last charge added.
*	=	Add 10 positive charges at random positions.
/	=	Remove last 10 charges.
]	=	Increase test charge density.
[	=	Decrease test charge density.
C	=	Toggle "Cap magnitude" option.
A	=	Toggle Animation mode.
E	=	Toggle Electric Field Vector line drawing.
M	=	Grab charge #1 with Mouse.
D	=	Debug mode. (Currently displays only the frame rate.)
T	=	Toggle Title screen overlay (program remains active).
F1	=	Toggle Help overlay (program remains active).
F2	=	Toggle Game Mode (try to hit the red target with the mouse)!
F3	=	Align charges in a Circle.
F4	=	Align charges in a Line along the left side of the screen (except mouse).
F5	=	Align charges in a Grid pattern (note: some charges may not be used).
F6	=	Randomize charge positions and set velocity to zero (except mouse).
F9	=	Green on black mode. (Default.)
F10	=	Black on white mode. (For printing screenshots.)

Instructions:

Start by using the preset modes. These modes can also be used when giving a presentation. Next, try lowering the test field density down to one test point, then click at various locations on the screen to place charges. Watch the effect on the electric field vector at the test point. You can drag and drop charges if you want to rearrange them. To turn the mouse back into a charge, click on a charge or press 'M'.

Notes:

There is a maximum of 200 charges.
Each charge is currently fixed at 10 coulombs!
The mouse is the purple charge or crosshair (big, white, plus sign).
During animation mode, charges are prevented from leaving the screen. They will bounce off the edge of the screen with a perfectly elastic collision.
Currently DirectX 3+ should work, but I will be using features in DirectX 5, so DirectX 5 will be required in the future.
Keep in mind that not all monitors have a 1:1 aspect ratio! If yours does not, then the screen may look "stretched" horizontally or vertically. This would cause, for example, a circle of charges to look like an ellipse.

Known problems/bugs:

Serious bug: The program may crash if you try to switch to another program while it is running. The computer, however, seems to remain stable.
I don't know what will happen if you try to run this program with a version of DirectX less than 5.
In animation mode, velocity and position are not modified infinity times per second, only once per frame (about 5-20 times per second). (For each frame, the current force on a charge is used to calculate acceleration, which is used to modify velocity [which is used to modify position].) I believe this causes energy to be added to the system.
Currently the Windows Line function is still used to draw the lines. This is relatively slow. I'd like to use DrawPrimitive (in DirectX 5) to draw the lines.
This program completely neglects forces due to magnetic or gravitational fields.
In animation mode, the effect of the electric field is assumed to have propagated at infinite speed, not the speed of light.
This program has mostly been evaluated by myself only, so there's bound to be more issues.

Fixed bugs:

A different value was used for the charges in animation mode than used when calculating the electric field vectors. This has been fixed.
The program used to flicker on some systems. This has been fixed.
I was using a very slow method to draw the lines. This has been fixed.
The capping of magnitude was a cap on the amount any one charge could contribute, not a cap on the final combined magnitude. This has been fixed.
Initially, animation mode did not track velocity (kinetic energy was lost every frame). It was simply adding the force vector! This has been fixed.
Charges were sequentially modified during animation mode, NOT per time slice! (In other words, two equal charges next to each other would not affect each other equally; one would be changed first, then the other would be affected by the already changed charge.) This has been fixed.

Web Site: wdell.com