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Variable capacitor

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:
3D extrusion electrostatics.

Geometry:

Given:
Relative permittivity of air ε = 1,
Potential difference ΔU = 1000 V

Problem:
Find the mutual capacitance between two stators as a function of the rotor position.

Solution:

QuickField simulation gives stored electric energy value W. With known potential difference ΔU the capacitance then can be calculated as C = 2W / ΔU2.

Results:

Rotating angle α

Energy W

Capacitance C

1.29e-6 J

2.58e-12 C

30°

2.25e-6 J

4.50e-12 C

60°

2.97e-6 J

5.94e-12 C

90°

3.22e-6 J

6.44e-12 C

See the variable_capacitor.pbm problem in the Examples folder.