RLC circuits are circuits that contain an ohmic resistor R, an inductor L and 
a capacitor C connected in series or parallel and connected to an alternating current 
source as shown in the following figures.It can be 
defined as "the impedance or resistance encountered by an alternating current when 
passing through the coil due to its self-induction" and its unit is ohm. Factors on 
which the inductive reactance of a coil (XL) depends:
? frequency (f)
? Coefficient of self-inductance of the coil (L)
 XL = 2? f L ----------------------------(1)
It is clear from this equation that the relationship between 
the inductive reactance and the frequency is a direct 
relationship, as the inductive reactance of the coil 
increases with increasing the frequency. When alternating current passes through the capacitor, it winds up a type of 
resistance called the "capacitive reactance of the capacitor" because it arises from 
the capacitance of the capacitor and is denoted by the symbol "XC".The 
alternating voltage and alternating current are in phase, that is, they have the same 
phase angle
When alternating current passes through an induction coil (without 
resistance), the coil's self-induction generates a reverse induced electromotive 
force in the coil that resists the original current, and this resistance is called the 
"inductive reactance of the coil" and is symbolized by the symbol (XL).Series connection Parallel connection
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When alternating current passes through the ohmic resistance, it encounters 
resistance as a result of the collision of the current's electrons with the conductor's 
atoms and molecules, and energy is exhausted in it in the form of heat.