🔋

Capacitors Overview and Types

Aug 30, 2025

Overview

This lecture introduces capacitors, their types, properties, schematic symbols, how they work, charging/discharging behavior, and relevant formulas for electronics applications.

Types of Capacitors

  • Capacitors store electrical charge and act somewhat like small batteries.
  • Electrolytic capacitors are polarized and must be connected with the correct positive (anode) and negative (cathode) leads.
  • Electrolytic capacitors usually have a long lead for positive and a stripe indicating the negative side.
  • All capacitors have a voltage rating, which is the maximum voltage they can safely handle.
  • Ceramic disc capacitors are not polarized and can be connected either way in a circuit.
  • Polyfilm (film) capacitors are also not polarized and can be connected in any orientation.

Capacitor Schematic Symbols

  • Non-polarized capacitors use a symbol with two parallel straight lines.
  • Polarized capacitors (like electrolytic) use a symbol with one straight line (anode) and one curved line (cathode).

Capacitance and Units

  • Capacitance is the ability to store charge, measured in farads (F).
  • Practical electronics often use microfarads (μF, 1μF = 0.000001F) and nanofarads (nF, 1nF = 0.000000001F).
  • A full farad is much larger than typically needed in hobby electronics.

How Capacitors Work

  • A capacitor has two conductive plates separated by a thin insulating (dielectric) layer.
  • When connected to a battery, one plate becomes positively charged and the other negatively charged.
  • Removing the battery leaves the plates with a charge difference, which can power a circuit briefly.
  • No current flows directly through a capacitor; rather, charge movement around the circuit creates current.

Time Constant (RC Circuit)

  • The RC time constant (Ï„) equals resistance (R, in ohms) times capacitance (C, in farads): Ï„ = R × C.
  • The time constant Ï„ is the time taken to reach about 63% of full charge.
  • After four time constants (4Ï„), the capacitor is nearly fully charged (about 98%).

Capacitors in Series and Parallel

  • Total capacitance in series: 1/C_total = 1/C1 + 1/C2 + ... (like resistors in parallel).
  • Total capacitance in parallel: C_total = C1 + C2 + ... (like resistors in series).

Key Terms & Definitions

  • Capacitor — An electronic component that stores and releases electrical charge.
  • Electrolytic Capacitor — A type of polarized capacitor with higher capacitance.
  • Ceramic Disc Capacitor — A non-polarized capacitor shaped like a disc.
  • Farad (F) — Unit of capacitance.
  • Microfarad (μF) — One millionth of a farad.
  • Nanofarad (nF) — One billionth of a farad.
  • RC Time Constant (Ï„) — The product of resistance and capacitance; time to charge to 63%.
  • Anode/Cathode — Positive/negative leads of polarized components.

Action Items / Next Steps

  • Research more about the technical definition and applications of the farad unit.
  • Await future lessons for safe capacitor circuit integration and advanced uses.

Full transcript