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Two different symbols for capacitors used in circuit diagrams are shown below:
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.
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.
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
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.
When beginning electronics, the type of polarised capacitors that are used are usually of the electrolytic type shown below:
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:
Some non-polarised capacitors are shown below:
Non-polarised capacitors are usually in the nano-Farad and pico-Farad ranges, e.g. 10nF, 100nF, 220nF, 100pF