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Starting electronics
Figure 4.3
(Left) an axial capacitor and (right) a radial capacitor
Measuring up
Capacitance values are measured in a unit called the farad
(named after the scientist: Faraday) and given the symbol:
F. We’ll define exactly what the farad is later, suffice to say
here that it is a very large unit. Typical capacitors have values
much, much smaller. Fractions such as a millionth of a
farad (that is, one microfarad: 1 µF), a thousand millionth
of a farad (that is, one nanofarad: 1 nF), or one million millionth
of a farad (that is, one picofarad: 1 pF) are common.
Sometimes, like the Ω or R of resistances, the unit F is omitted
— 15 n, instead of 15 nF, say.
The circuit for our first experiment is shown in Figure 4.4. You
should see that it bears a striking resemblance to the voltage
divider resistor circuits we looked at last chapter, except that
a capacitor has taken the place of one of the resistors. Also
included in the circuit of Figure 4.4 is a switch. In the last
chapter’s circuits, no switch was used as we were only interested
in static conditions after the circuits were connected.
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