Fixed and Variable Capacitors
Safety Warnings
Warning: Discharged Capacitors
Purpose
Displays a collection of commercial fixed and variable capacitors to show how geometry, dielectric material, and voltage rating affect capacitance and physical size. Students see that capacitance does not correlate simply with size, and examine how manufacturers maximize \(C = \varepsilon_0 \varepsilon_r A/d\) in compact packages.
Figure 1:
Assortment of fixed capacitors arranged for comparison. Physical size does not correlate simply with capacitance — the dissected rolled-foil capacitor (center) reveals internal construction.
Figure 2:
Power supply circuit board showing capacitors in context — electrolytic caps for bulk filtering, film caps for high-frequency decoupling.
Figure 3:
Variable capacitors. The open-frame unit (front) shows interleaved rotating plates — turning the shaft changes plate overlap area and thus capacitance. The large enclosed unit (rear) is similar in principle.