# Like-Charge Dipole (esChargedSpheresT.pre)

Keywords:

electrostatics, like-charge dipole

## Problem description

This ike-charge Dipole simulation computes the electrostatic potential and field for a dipole of two spheres with given radius, at the same potential.

This simulation can be performed with a VSimEM or VSimPD license.

## Opening the Simulation

The like-charge dipole example is accessed from within VSimComposer by the following actions:

• In the resulting Examples window expand the VSim for Electromagnetics option.
• Expand the Electrostatics (text-based setup) option.
• Select Like-charge Dipole (text-based setup) and press the Choose button.
• In the resulting dialog, create a New Folder if desired, and press the Save button to create a copy of this example.

The basic variables of this problem should now be alterable via the text boxes in the left pane of the Setup Window, as shown in Fig. 213.

Fig. 213 Setup Window for the Like-charge Dipole example.

## Input File Features

The input file allows one to choose the location,radius and electrostatic potential of the spheres. It is also possible to adjust the size of the simulation domain, start point (m) of the simulation in the X direction, resolution (number of cells) in the simulation domain and number of dimensions to run the simulation in. The length of one timestep, DT is also available for modification. As the simulation is electrostatic it does not matter what value is selected for DT.

## Running the simulation

After performing the above actions, continue as follows:

• Proceed to the Run Window by pressing the Run button in the left column of buttons.
• To run the file, click on the Run button in the upper left corner of the Logs and Output Files pane. You will see the output of the run in this pane. The run has completed when you see the output, “Engine completed successfully.” This is shown in Fig. 214.

Fig. 214 The Run Window at the end of execution.

## Visualizing the results

After performing the above actions, continue as follows:

• Proceed to the Visualize Window by pressing the Visualize button in the left column of buttons.

The electrostatic potential can be viewed as follows:

• Expand Scalar Data
• Select Phi
• Select Display Contours
• Select the Clip All Plots check box
• Move the time slider forward to Dump 1

Fig. 215 shows the visualization seen.

Fig. 215 Visualization of like-charge dipole as a pseudocolor plot.

## Further Experiments

Change the distance between spheres by changing XPOS1 and XPOS2, and see how the electric field changes.

Change the sphere radius RADIUS and see how the electric field changes.

Change the sphere’s potential to observe a change in the electric field.

Determine how the electric field changes with varying resolution.

To reduce computational time NDIM can be switched to 2 to make it a 2D simulation.