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Resistors in a parallel circuit are a little
more difficult. The formula to use is:
Capacitors behave exactly the opposite to resistors:
when capacitors are in parallel, you add them:
Capacitors in series, on the other hand, are similar
to resistors in parallel. You add the reciprocals:
Capacitors can pass alternating current
(AC) signals while blocking direct current (DC) signals. They
can also store electricity or act as filters to smooth out pulsating
signals. Very small capacitors are usually used in high-frequency
applications, such as radios, transmitters and oscillators.
Very large capacitors normally store electricity or act as filters.
The unit of capacitance (electricity storage
capacity) is expressed in farad, which is an extremely large
amount of electricity and too large a unit to use in practice.
Commonly used smaller units are the microfarad (abbreviated
µF), nanofarad (nF) and picofarad (pF). The section on decimal
multipliers shows the relationship between these. Some capacitance
values are commonly expressed by only one unit while others
can be expressed by two or more units, e.g. 1µF would rarely
be called 1000nF and never 1,000,000pF, even though these are
equivalent. However, 0.0047 µF is often expressed as 4.7nF,
or as 4700pF. If the value contains a decimal point the µ, n
or p is sometimes put in place of the decimal point. Therefore
a 4.7pF capacitor can be marked as 4p7F. farad |
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