Analysis of RC Circuit

Analysis of Series RC Circuit

 

Ohm's Law and Kirchoff's Law are used in the analysis of a series RC circuit. Ohm's Law, when applied to a series RC circuit, involves the use of quantities of Z, U, and I. The three equivalent forms of Ohm's Law are shown above. From Kirchoff's voltage law, the sum of the voltage drops equals the source voltage (U_s). Since U_R and U_C are 90^o out of phase, the magnitude of the source voltage is expressed by the voltage triangle as shown in the illustration.  

Analysis of Parallel RC Circuit

 

The source voltage appears across both the resistive and the capacitive branches. Therefore, U_s, U_R and U_c are all in phase and of the same magnitude. In a parallel circuit, each branch has its individual current. The resistive branch current I_R is in phase with U_s, but the capacitive branch current I_c leads U_s by 90^o. By Kirchoff's current law, the total current is the phasor sum of the two branch currents. The impedance of a parallel circuit equals the applied voltage divided by the total current Z_eq = U_s / I.