Obtain the equivalent capacitance of the network in Fig. 2.35. For a 300 V supply, determine the charge and voltage across each capacitor.

Capacitance of capacitor C1 = 100pF, C2 = 200pF, C3 = 200 pF, C4 = 100 pF.


Supply potential (V) = 300 V


Let the equivalent capacitance of capacitors C2 and C3(connected in series) be C'.



C’ = 100pF


Let the equivalent capacitance of capacitors C1 and C’(connected in parallel) be C’’.


C’’ = C’ + C1 = 100 + 100 = 200pF


Let the equivalent capacitance of C’’ and C4 (connected in series) be C’’’.



C’’’ = 200/3pF


Thus, the equivalent capacitance of the circuit = 200/3 pF.


Now, Supply potential (V) = 300 V


Charge on C4 is given by,


Q4 = C’’’V = = 2 × 10-8C


So, V4 = Q4/C4 = (210-8)/(10010-12) = 200C


Potential difference across C1 is given by, V1 = V-V4 = 300-200 = 100V


Charge on C1 is given by, Q1 = C1V1 = 100 × 10-12 × 100 = 10-8C


C2 and C3 having same capacitances have a potential difference of 100 V together.


Since C1 and C3 are in series, the potential difference across C2 and C3 is given by,V2 = V3 = 50V


Therefore charge on C2 is given by,Q2 = C2V2 = 20010-1250 = 10-8C


And charge on C3 is given by,Q3 = C3V3 = 20010-1250 = 10-8C.


The charge and voltage across each capacitor are as follows:


Q1 = 10-8 C



V1 = 100V



Q2 = 10-8 C



V2 = 50V



Q3 = 10-8 C



V3 = 50V



Q4 = 210-8 C



V4 = 200V



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