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Main >> Applications >> Sample problems >> Collinear cylinders capacitance
Find the mutual capacitance between two collinear infinitely long cylinders.
Problem Type:
Plane problem of electrostatics.
Geometry:
a = 5 mm, b = 10 mm.
Given:
Relative permittivity of air ε = 1,
The charge q = 1 nC.
Task:
Find the mutual capacitance between two collinear infinitely long cylinders and compare it with analytical solution:
C = 2πεε_{0} * l / ln(a/b) [F]. *
Solution:
Each of the conductor's surface is marked as 'floating conductor', i.e. isolated conductors with unknown potential. At some point on each of conductor's surface the charge is applied. The charge is then redistributed along the conductor surface automatically.
Results:
Potential distribution between collinear cylinders.
The capacitance can be calculated as C = q / (U2  U1). The measured potential difference is U2U1 = 12.459 V.
The capacitance is C = 10^{9} / 12.459 = 8.027·10^{11} F.
QuickField 
Theoretical result 

C, pF 
80.27 
80.26 