# RC Circuit

**Definition:** The combination of a pure resistance R in ohms and pure capacitance C in Farads is called RC circuit. It is also called first order RC circuit and is used to filter the signals by passing some frequencies and blocking other.

**RC Series Circuit
**

A circuit containing resistance and capacitance connected in series together is called **an RC series circuit.**

**Steps to draw a phasor diagram for an RC circuit**

- Current I is taken as reference
- Voltage drop in resistance is (
**V**_{R}).

** V _{R} = IR** is drawn in phase with the current I

- Voltage drop in capacitive reactance is
**(V**_{C}).

** V _{C} = IXC** and is drawn 90° behind the current (as current leads the voltage

by 90° in pure capacitive load circuit).

- The vector sum of the two voltage drops is equal to the applied voltage (V).

Now in right angle triangle OMN

V = √(V_{R)2+(VC)2}

V = √(IR) ^{2 }+ (IX_{C}) ^{2}

V = I √R^{2} + X^{2}_{C}

I = V/√R^{2} +X^{2}_{C} = V/Z

Where Z= √R^{2} +X^{2}_{C}

Z is known as **impedance** of the circuit and is defined as the total opposition offered to the flow of current in an RC series circuit. It is measured in ohms.