AC1 Fundamentals Unit 7 – Capacitive Reactance
UNIT 7 – CAPACITIVE REACTANCE
UNIT OBJECTIVE
At the completion of this unit, you will be able to determine the characteristics of resistive-
capacitive (RC) circuits by using an oscilloscope and given information.
UNIT FUNDAMENTALS
There are many similarities and differences between capacitive reactance (XC) and inductive
reactance (XL). They work oppositely to each other in many respects when subjected to an ac
signal.
The amount of opposition a capacitor (C) offers to ac circuit current is measured by the
resistance it offers to the power source (Vac).
Vac
XC =
IC1
This apparent resistance is called capacitive reactance(XC) and is measured in ohms.
If capacitance increases (larger capacitor value), capacitive reactance (XC) decreases; if
capacitance decreases, XC increases.
Increases in the frequency of the power source (Vac) decrease capacitive reactance (XC); if
frequency decreases, XC increases.
Capacitive reactance (XC) does not depend on the amplitude of the power source.