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 (VR).
VR = IR is drawn in phase with the current I
- Voltage drop in capacitive reactance is (VC).
VC = 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 = √(VR)2+(VC)2
V = √(IR) 2 + (IXC) 2
V = I √R2 + X2C
I = V/√R2 +X2C = V/Z
Where Z= √R2 +X2C
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.