Capacitors and Ohm's law

What are the types of capactor

A capacitor is an electronic component that stores and releases electrical energy in a circuit. It consists of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied across the plates, an electric field is created, causing the capacitor to store energy.

There are two main types:

Electrolytic capacitors – these are polarised, so they have a positive and a negative leg.
Usage: applications requiring large capacitance values, such as timing circuits and power supplies.
Ceramic capacitors – these are non-polarised.
Usage: applications like signal smoothing.

Circuit symbols

Two parallel lines of equal length. These lines represent the two plates of the capacitor — Figure caption,
The symbol for a ceramic (non-polarised) capacitor

Photo of an orange ceramic capacitor labelled 104 — Image caption,
A ceramic capacitor

Two parallel lines of equal length. These lines represent the two plates of the capacitor. A + indicates the positive terminal — Figure caption,
The symbol for an electrolytic (polarised) capacitor

A photograph of a black electrolytic capacitor with 10μF and 160c printed on it — Image caption,
An electrolytic capacitor

What are capacitors used for?

Choose capacitors based on the required capacitance, voltage rating, and whether the circuit requires a polarised or non-polarised capacitor.

Units of Capacitance:

Farads (F): The basic unit of capacitance.
For a typical small voltage circuit, a Farad is quite large so Microfarads (µF) or Nanofarads (nF) are more likely to be used. The bigger the value of the capacitor, the longer it takes to charge/discharge!
Microfarads (µF): 1µF = 0.000001F (10⁻⁶)
Nanofarads (nF): 1nF = 0.000000001F (10⁻⁹)
Picofarads (pF): 1pF = 0.000000000001F (10⁻¹²)

Examples of capacitors in a circuit

Circuit diagram containing a capacitor, resistor, an LED, a SPDT switch and a 9v battery — Figure caption,
An example diagram of a capacitor being used in a circuit

Stage 1: The 9V battery sends electrical charge to the capacitor's plates, allowing it to store energy (like filling a tank). The capacitor continues charging until it's full.

Stage 2: When the is manually pressed, the battery is now cut off from the rest of the circuit. However, the stored energy from the capacitor can now flow through the circuit, making the LED light up briefly. The resistor will control the discharge rate of the capacitor by limiting the flow of current through the circuit.