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The ultimate quick guide to capacitors, benefits and uses

19 April 2021

As technology advances, capacitors are to be found in increasingly more electronic devices, offering several benefits to users. Discover what they are, what they do and their many benefits through this quick guide.

What are capacitors?

Originally known as a condenser, a capacitor is a passive two-terminal electrical component that stores energy electrostatically in an electric field. Invented in 1745 by Ewald Georg von Kleist of Pomerania in Germany, capacitors are used in almost all electrical applications today. All capacitors contain a minimum of two electrical conductors separated by a dielectric. Thin films of metal, disks or aluminium can act as conductors, whereas glass, plastic film, ceramic, air and paper can act as a dielectric.

Capacitors differ from resistors in that they do no dissipate energy, rather they store energy in the form of an electrostatic field between plates. And although capacitors are similar to a battery, they can release charge much faster. The storage amount depends on what is known as capacitance, measured in Farads (F).

The basic composition of a capacitor

  • At the top and bottom of a capacitator are a set of metal plates (conductors) –attractive to electric charges.
  • In the middle of the metal plates is an insulator (dielectric) – not attractive to electricity.
  • The metal plates at the top and bottom are connected by two terminals which connect it to the rest of the circuit. One end connects to power, the other flows to the ground.
A range of different capacitors on table
Different types of capacitors

Benefits of capacitors

Capacitors come with many benefits, including:

  • Storing energy directly onto the plates makes charging and discharging a lot faster
  • Capacitors effectively filter out unwanted frequencies
  • Capacitors can almost instantaneously discharge current
  • Capacitors are less sensitive to temperature
  • Capacitors can effectively handle power loss and make power production more economical
  • Capacitors life cycles can last 10-15 years
  • Capacitors can handle high voltage applications, making them suitable for high-frequency uses

Different types of capacitors

Capacitors come in many shapes and sizes, below are some different types:

Ceramic capacitor

Ceramic capacitors hold a smaller charge and leak less current than their electrolytic counterparts. They are also the cheapest type out of the bunch. These types of capacitors are also easy to identify – simply look for a tiny yellow or red bulb with two terminals.

Electrolytic capacitors

Resembling small tin cans found on a circuit board, electrolytic capacitors can hold large electric change. This is the only type of capacitor that is polarized, and they only work when wired to a particular orientation. Electrolytic capacitors contain a positive pin (anode), connected to a higher voltage, and a negative pin (cathode). Electrolytic caps should not be your first choice when needing to store energy, as these capacitors are known for leaking current quicker than ceramic caps.

Supercapacitors 

As their name suggests, supercapacitors are great at storing high amounts of energy. Unlike electrolytic capacitors, however, these types of capacitors are used to store and discharge energy similar to batteries. Supercapacitors differ from batteries in that they release all their charge at once.

Capacitors fitted on electric board
Capacitors can be found in a wide range of electrical applications

Applications of capacitors

From electronics like fans to electrical cars, capacitors can be found everywhere. Some applications include:

Energy storage

When connected to its charging circuit, a capacitor can store energy. When disconnected, it can dissipate that stored energy. Capacitors are found in many electronic devices, helping maintain the power supply when batteries are being charged.

Sensors 

Capacitors can be used as sensors to measure everything from air humidity to mechanical strain. In sensing applications, they can be used to measure the distance between the parallel plates and the material between them. The first can detect mechanical changes like acceleration and pressure.

Power conditioning

Capacitors can be used in the conditioning of power supplies. Capacitors let AC currents pass yet block DC currents when they are charged, known as “Capacitor Coupling”. By splitting these two signal types, capacitors can clean the supply of power.

Signal processing

Dynamic Random Access Memory (DRAM) uses capacitors to display binary information as bits. When charged, the device reads one value and when discharged, it reads another. You can also find capacitors in Charge-Coupled Devices (CCDs) in analogue form and in conjunction with inductors to tune circuits to specific frequencies.

Tips on capacitor selection

When choosing a capacitor, here are some things to consider:

  • Capacitor size. This refers to the capacitor’s physical size and total capacitance.
  • Capacitor tolerance. This refers to the capacitor’s variable tolerance, which can vary between ±1% to ±20% of its advertised value.
  • Maximum voltage. Every capacitor has a maximum voltage, this can range anywhere from 1.5V to 100V.
  • ESR (Equivalent series resistance). The terminals on a capacitor have a tiny level of resistance. Be mindful of heat and power loss to avoid running into problems.
  • Leakage current. Pay attention to how much your capacitors leak their stored charge.

Popular capacitator categories on Marketplace 

There’s a range of different capacitors listed on Marketplace. Let the links below guide you or use the simple search tool on the site. Want to take a short cut? View all capacitors currently listed by clicking here to see the full range.

Brand Product name Manufacturer Code
Vishay Vishay Cap Tant Wet 10uF 50V 10% (5.56 X 13.08mm) Axial (0.01%FR) 125°C M39006/22-0565
Sprague Sprague Cap Tant Solid 15uF 75V 10% (8.92 X 19.96mm) Axial (1%FR) 125C Bulk M39003/01-2421

 

 

KEMET KEMET Cap Tant Solid 100uF 10V 10% (7.34 X 17.42mm) Axial (0.001%FR) Bulk M39003/01-2981

 

BHS BHS BATTERY CAPACITOR RELIANCE 121724500

 

AVX AVX Cap Ceramic 68pF 500V +140±25ppm/C 5% Axial 125°C CY10C680J