Practical takeaway
A capacitor stores energy in an electric field. In practical radio circuits it can block DC, pass changing signals, filter power supplies and help tune circuits.
Electricity & Electronics
Capacitors
Watch a component store electrical energy in an electric field and then release it.
TECHNICIAN FOUNDATION8 of 16
Technician exam focus
Know that capacitance is measured in farads and recognize common capacitor functions and schematic symbols.
A temporary store of electrical energy
Two conductors separated by an insulator
A capacitor stores energy in the electric field between its plates. When it charges, equal and opposite charge builds on the two plates.
Capacitance is measured in farads.
Radio and electronics circuits commonly use microfarads (µF), nanofarads (nF), and picofarads (pF).
Charging current does not stay constant.
Current is greatest at the start of charging, then falls as capacitor voltage approaches the source voltage. During discharge, current flows in the opposite direction and also falls toward zero.
Why hams care
Capacitors are used for coupling, bypassing, filtering, timing, and tuning. Their opposition to AC changes with frequency.
STEMulation
Charge and discharge
How to use it: set the relative capacitance, then click Charge or Discharge. A larger demo value changes more slowly. The graph runs once and stops so you can inspect the curve.
Charge0%
Voltage0.0 V
Current behaviornone
The trace is intentionally held at the end of each run. Charge again or discharge to start a new curve.