It is simply a number associated with a point in space. That tells us that electric potential shows us the potential energy per unit charge. A helpful way to think about it is by considering it's unit, that is Joules/Couloumb. Didn't have time today to put this into the Chimera daily build.Allow me to explain a couple of concepts.įirstly, you must understand what electric potential is. > I made a Python Chimera script to show electrostatic field lines using a potential map. National Institute of Allergy and Infectious Diseases shall not accept liability for any statements made that are sender's own and not expressly made on behalf of the NIAID by one of its representatives. If you have received this e-mail in error please inform the sender and delete it from your mailbox or any other storage devices. It should not be used by anyone who is not the original intended recipient. > Disclaimer: The information in this e-mail and any of its attachments is confidential and may contain sensitive information.
> Bioinformatics and Computational Biosciences Branch (BCBB) > This is fantastic! I noticed that you've even colored the lines by their potential. On Dec 13, 2012, at 5:37 AM, "Hurt, Darrell (NIH/NIAID) " wrote: > obviously many lines to choose from, but your image shows lines > Just out of curiosity, how are the field lines chosen? There are > would be handy depending on what one wants to show. > better approaches and probably different field line choosing methods > around charges and more around bigger charges. But it still seems to concentrate field lines > potential close to the charge is not q/r - no singularity at the > distribution for each charge (it uses atom radius I think). > this morning the APBS potential probably uses a Gaussian charge > are grid points where q/r**3 > C, in other words r**3 > number of grid points around a charge used is proportional to the If the chosen points have grad squared / potential > C then they
> squared divided by the potential is q/r**3 ( = (q/r**2)**2 / (q/r) Near a point charge the potential is q/r. > largest N values for starting N field lines. > potential at every grid point and use the grid points with the > So I compute the magnitude of the gradient squared divided by the > originate around charges and the number of lines around a charge to > just depends on which you choose to show. > the lines is given by how dense they are in different regions. > which of the infinity of lines to show. This is the whole problem with showing field lines. There is some trickiness to which field lines are shown that is described in the email below to Conrad. The lines parameter is how many lines to show, with lines starting at potential magnitudes above 10 (startAbove). The measure command creates the lines and the scolor command colors them. Scolor #1 volume #0 cmap -10,red:0,white:10,blue Measure fieldLines #0 lines 500 startAbove 10 color pink linewidth 2 The code is slow (10 seconds for 1000 lines of a 100**3 potential map) and I'd like to make some other improvements, but I put it in as is so you can try it right away if you like. It will be in tonight's Chimera daily build but not in the Chimera 1.7 release candidate. Ok I checked in the electrostatic field line code. Previous message: Electric field lines?.Electric field lines? Tom Goddard goddard at