Variable capacitor
QuickField simulation example
Variable air capacitor consists of fixed stator plates and movable rotor. Capacitance between the stator plates depends on the position of the rotor.
Problem Type electrostatics.
Geometry 3D extrusion.
Given
Relative permittivity of air ε = 1,
Potential difference ΔU = 1000 V
Task
Find the mutual capacitance between two stators as a function of the rotor position.
Solution
QuickField simulation gives energy W and electric potential U distribution. The capacitance then can be calculated as C = 2W / ΔU².
Results
| Rotating angle α | Energy W | Capacitance C |
| 0° | 1.29 uJ | 2.58 pC |
| 30° | 2.25 uJ | 4.50 pC |
| 60° | 2.97 uJ | 5.94 pC |
| 90° | 3.22 uJ | 6.44 pC |
- Video: Variable capacitor. Watch on YouTube
- Download simulation files (files may be viewed using any QuickField Edition).