The Maplin Electronic Circuits Handbook, 2nd Edition

22 PASSIVE COMPONENTS

Where X

c

is the reactance in Ω, / is the frequency in Hz, and C is the

capacitance in F.

As an example, consider the case of a lOOnF capacitor which forms

part of a filter connected across a 240 V 50 Hz mains supply. The reactance

of the capacitor will be:

X

c

= - -— = 31.8 kü

c

2π50 χ 100 χ 10

The r.m.s. current flowing in the capacitor will thus be:

240

/

c

= —= 7.55 mA

High frequency effects

Like resistors, capacitors possess stray lead inductance. This has the effect

of presenting a resonant L-C circuit in which the stray inductance of the

leads becomes series resonant with its own capacitance. The self-resonant

frequenc ...