Language:

Main >> Applications >> Sample problems >> Nonconcentric spheres capacitance
Problem Type:
Axisymmetric problem of electrostatics.
Geometry:
a = 100 mm, d = 500 mm.
Given:
Relative permittivity of vacuum ε = 1,
The charge q = 10^{9} C
Task:
Find the mutual capacitance between two spheres and compare its value with analytical solution:
C = 2π·ε·ε_{0} · a [F] *,
where D = d/ (2a).
Solution:
Sphere's surfaces are marked as 'floating conductor', i.e. isolated conductors with unknown potential. At some point on each of sphere's surface the charge is applied. The charge is then redistributed along the conductor surface automatically.
Results:
Potential distribution around spheres.
The capacitance can be calculated as C = q / (U2  U1). The measured potential difference is U2  U1 = 143.4 V.
The capacitance is C = 10^{9} / 143.4 = 6.97·10^{12} F.
QuickField 
Theoretical result  
C, pF 
6.97 
6.99 
View simulation report in PDF.
Download simulation files (files may be viewed using any QuickField Edition).