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Capacitor

Created on: 30 July 2012

Two different symbols for capacitors used in circuit diagrams are shown below:

Capacitor schematic symbols

The symbol on the left represents a polarised capacitor – it has a positive and negative lead.

The symbol on the right represents a non-polarised capacitor – it can be connected either way around in a circuit.

Capacitance

Capacitors have values that are give in Farads (symbol F). Capacitors used in electronics are usually in the micro-Farad, nano-Farad or pico-Farad ranges.

Examples:

A ten micro-Farad capacitor is written as 10µF or 10uF

A one-hundred nano-Farad capacitor is written as 100nF or just 100n. It may be marked as 0.1 (meaning 0.1uF which is 100nF). Or it may be marked with 104, meaning 10 and four zeros: 100000pF which is equal to 100nF.

A twenty-two pico-Farad capacitor is written as 22pF or 22p

Voltage

Capacitors have a voltage rating, e.g. 16V, 50V. The higher the voltage rating, the bigger the physical capacitor will usually be. When using capacitors in a 9V circuit, they must be rated at 16V or more.

Polarised Capacitors

When beginning electronics, the type of polarised capacitors that are used are usually of the electrolytic type shown below:

Electrolytic capacitors

Electrolytic capacitors are mostly in the micro-Farad range, e.g. 10uF, 220uF, 470uF

The polarity of an electrolytic capacitor is marked on the capacitor body – the negative lead of the capacitor is marked. The longer lead of the electrolytic capacitor is the positive lead:

Electrolytic capacitor polarity

Non-polarised Capacitors

Some non-polarised capacitors are shown below:

Non-polorised capacitors

Non-polarised capacitors are usually in the nano-Farad and pico-Farad ranges, e.g. 10nF, 100nF, 220nF, 100pF